Tag Archives: clariion

Using Cloud as a SAN Tier?

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I came across this press release today from a company that I wasn’t familiar with and immediately wanted more information.  Cirtas Systems has announced support for Atmos-based clouds, including AT&T Synaptic Storage.  Whenever I see these types of announcements, I read on in hopes of seeing real fiber channel block storage leveraging cloud-based architectures in some way.  So far I’ve been a bit disappointed since the closest I’ve seen has been NAS based systems, at best including iSCSI.

Cirtas BlueJet Cloud Storage Controller is pretty interesting in its own right though.  It’s essentially an iSCSI storage array with a cache and a small amount of SSD and SAS drives for local storage.  Any data beyond the internal 5TB of usable capacity is stored in “the cloud” which can be an onsite Private Cloud (Atmos or Atmos/VE) and/or a Public Cloud hosted by Amazon S3, Iron Mountain, AT&T Synaptic, or any Atmos-based cloud service provider.

Cirtas BlueJet

The neat thing with BlueJet is that it leverages a ton of the functionality that many storage vendors have been developing recently such as data de-duplication, compression, some kind of block level tiering, and space efficient snapshots to improve performance and reduce the costs of cloud storage.  It seems that pretty much all of the local storage (SAS, SSD, and RAM) is used as a tiered cache for hot data.  This gives users and applications the sense of local SAN performance even while hosting the majority of data offsite.

While I haven’t seen or used a BlueJet device and can’t make any observations about performance or functionality, I believe this sort of block->cloud approach has pretty significant customer value.  It reduces physical datacenter costs for power and cooling, and it presents some rather interesting disaster recovery opportunities.

Similar to how Compellent’s signature feature, tiered block storage, has been added to more traditional storage arrays, I think modified implementations of Cirtas’ technology will inevitably come from the larger players, such as EMC, as a feature in standard storage arrays.  If you consider that EMC Unified Storage and EMC Symmetrix VMAX both have large caches and block- level tiering today, it’s not too much of a stretch to integrate Atmos directly into those storage systems as another tier.  EMC already does this for NAS with the EMC File Management Appliance.

Conceptual Diagram

I can imagine leveraging FASTCache and FASTVP to tier locally for the data that must be onsite for performance and/or compliance reasons and pushing cold/stale blocks off to the cloud.  Additionally, adding cloud as a tier to traditional storage arrays allows customers to leverage their existing investment in Storage, FC/FCoE networks, reporting and performance trending tools, extensive replication options available, and the existing support for VMWare APIs like SRM and VAAI.

With this model, replication of data for disaster recovery/avoidance only needs to be done for the onsite data since the cloud data could be accessed from anywhere.  At a DR site, a second storage system connects to the same cloud and can access the cold/stale data in the event of a disaster.

Another option would be adding this functionality to virtualization platforms like EMC VPLEX for active/active multi-site access to SAN data, while only needing to store the majority of the company’s data once in the cloud for lower cost.  Customers would no longer have to buy double the required capacity to implement a disaster recovery strategy.

I’m eagerly awating the implementation of cloud into traditional block storage and I can see how some vendors will be able to do this easily, while others may not have the architecture to integrate as easily.  It will be interesting to see how this plays out.

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EMC, Isilon, and CSX possibilities..

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As you’ve no doubt heard, EMC has completed the tender offer to acquire Isilon (www.isilon.com)  for a Cajillion dollars (actually ~$2 Billion) and some people are asking why.  From where I sit, there are many reasons why EMC would want a company like Isilon, ranging from it’s media-minded customer base, to the technical IP, like scale-out NAS, that sets Isilon apart from the rest.

This EMC Press Release, as well as this one, and Chucks Blog are some of the many places to find out more about the acquisition…

I was thinking a lot about that technology as I worked on a high-bandwidth NAS project with a customer recently.  Isilon’s primary product is an IP-based storage solution that uses commodity based hardware components, combined with their proprietary OneFS Operating System, to deliver scale-out NAS with super simple management and scalability.  A single Isilon OneFS based filesystem can scale to over 10PB across hundreds of nodes.  Isilon also provides various versions of hardware that can be intermixed to increase performance, capacity, or both depending on customer needs.  You don’t necessarily have to add disks to an Isilon cluster to increase performance.

When looking at EMC’s own product line, you’ll find that Atmos delivers similar scale-out clustering for object-based storage, while VMAX does a similar type of scaling for high-end block storage (FC, FCoE, and iSCSI), and Greenplum provides scale-out analytics as well.  Line up Isilon’s OneFS, EMC GreenPlum, EMC Atmos, and EMC VMAX, and we can now deliver massive scale-out storage for database, object, file, and block data.  With VPLEX and Atmos, EMC also delivers block and object storage federation across distance.

Isilon’s OneFS also has technologies that mirror EMC’s but are implemented in such a way as to leverage the Scale-Out NAS model.  Take FlexProtect, for example, which is Isilon’s data protection mechanism (similar to RAID) and allows admins to apply different protection schemes (N+1 ala RAID5, N+2 ala RAID6, N+3, and even N+4 redundancy) on individual files and directories.  SmartPools, which is policy based, automatically tiers data at a file level based on read/write activity across different protection types and physical nodes, similar to how FASTVP tiers data at a block level on EMC Unified and VMAX.  Both EMC and Isilon realize that all data is not equal.

Rather than just repackage OneFS with an EMC logo (which I’m sure we’ll do at first), I wonder what else can we do with Isilon’s IP…

A recent series of blog posts by Steve Todd (Information Playground) on the topic of a Common Software Execution Environment (See CSX Technology and The Benefits of Component Assembly) got me thinking about deeper integration and how CSX can accelerate that integration.

For example…

What if EMC Engineering took the portions of code from Isilon’s OneFS that handle client load-balancing, file-level automated tiering, and flexible protection and turned them into CSX components.  Those components could be dropped into Celerra and immediately add Scale-Out NAS to EMC’s existing Unified storage platforms.  Or, imagine those components running directly in VMAX engines, providing scale-out NAS simultaneously with scale-out SAN across multiple, massive scale storage systems.  Combine the load balancing code and FlexProtect from Isilon with FASTVP in EMC Clariion to provide scale-out SAN in a midrange platform.

We could also reverse the situation and use the compression component that is in Clariion and Celerra, plus federation technology in Atmos, both added to OneFS in order reduce the storage footprint and extend Scale-Out NAS to many sites over any distance.  Add a GreenPlum component and suddenly you have a massive analytics cluster that spans multiple sites for data where you need it, when you need it.

The possibilities here really are endless, it will be very interesting to see what happens over the next 12 to 24 months.

Disclaimer: Even though I am an EMC employee, I am in no way involved in the EMC/Isilon acquisition, have no knowledge of future plans and roadmaps with regard to EMC and Isilon, and am not privy to any non-public information about this topic.  I am merely expressing my own personal views on this topic.

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Compression better than Dedup? NetApp Confirms!

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The more I talk with customers, the more I find that the technical details of how something works is much less important than the business outcome it achieves.  When it comes to storage, most customers just want a device that will provide the capacity and performance they need, at a price they can afford–and it better not be too complicated.  Pretty much any vendor trying to sell something will attempt to make their solution fit your needs even if they really don’t have the right products.  It’s a fact of life, sell what you have.  Along these lines, there has been a lot of back and forth between vendors about dedup vs. compression technology and which one solves customer problems best.

After snapshots and thin provisioning, data reduction technology in storage arrays has become a big focus in storage efficiency lately; and there are two primary methods of data reduction — compression and deduplication.

While EMC has been marketing compression technology for block and file data in Celerra, Unified, and Clariion storage systems, NetApp has been marketing deduplication as the technology of choice for block and file storage savings.  But which one is the best choice?  The short answer is.. it depends.  Some data types benefit most from deduplication while others get better savings with compression.

Currently, EMC supports file compression on all EMC Celerra NS20, 40, 80, 120, 480, 960, VG2, and VG8 systems running DART 5.6.47.x+ and block compression on all CX4 based arrays running FLARE30.x+.  In all cases, compression is enabled on a volume/LUN level with a simple check box and processing can be paused, resumed, and disabled completely, uncompressing the data if desired.  Data is compressed out-of-band and has no impact on writes, with minimal overhead on reads.  Any or all LUN(s) and/or Filesystem(s) can be compressed if desired even if they existed prior to upgrading the array to newer code levels.

With the release of OnTap 8.0.1, NetApp has added support for in-line compression within their FAS arrays.  It is enabled per-FlexVol and as far as I have been able to determine, cannot be disabled later (I’m sure Vaughn or another NetApp representative will correct me if I’m wrong here.)  Compression requires 64-bit aggregates which are new in OnTap 8, so FlexVols that existed prior to an upgrade to 8.x cannot be compressed without a data migration which could be disruptive.  Since compression is inline, it creates overhead in the FAS controller and could impact performance of reads and writes to the data.

Vaughn Stewart, of NetApp, expertly blogged today about the new compression feature, including some of the caveats involved, and to me the most interesting part of the post was the following graphic he included showing the space savings of compression vs. dedup for various data types.

Image Credit: Vaughn Stewart, NetApp

The first thing that struck me was how much better compression performed over deduplication for all but one data type (Virtualization will usually fare well because in a typical environment there are many VMs with the same operating system files).  In fact, according to NetApp, deduplication achieves very little savings, if any, for the majority of the data types here.
 
The light green bar indicates savings with both dedupe AND compression enabled on the same dataset.  In 5 out of 9 cases, dedup adds ZERO savings over compression alone.  I can’t help but wonder why anyone would enable dedup on those data types if they already had compression, since both features use storage array CPU resources to find and compress or dedup data.  I am aware that in some cases, dedup can improve performance on NetApp systems due to dedup-aware cache, but I also believe that any performance gain is directly related to the amount of duplication in the data.  Using this chart, virtualization is really the only place where dedup seems particularly effective and hence the only place where real performance gains would likely present themselves.
 
The challenge for NetApp customers will be getting their data into a configuration that supports compression due to the 64-bit aggregate requirement, lack of an easy and non-disruptive LUN migration feature (DataMotion appears to only support iSCSI and NFS and requires several additional licenses), and no way to convert an aggregate from 32-bit to 64-bit.  Once compression has been enabled, if there is truly no way to disable it, any resulting performance impact will be very difficult to rectify.
 
On the other hand, any EMC customer with current maintenance can upgrade their NS or CX4 array to newer versions of DART or FLARE, and compression can be enabled on any existing data after the fact.  If performance becomes an issue for a particular dataset once compressed, the data can be uncompressed later.  Both operations are completely non-disruptive and run in the background.  While block compression only works on LUNs in a virtual pool, as opposed to a traditional RAID group, enabling compression on a normal LUN will automatically migrate the LUN into a virtual pool, perform zero-page reclaim, followed by compression, and the entire process is completely non-disruptive to the application.  Oh, and compressed data can still be tiered with FASTVP across SSD, FC, and SATA disk and/or benefit from up to 2TB of FASTCache.
 
I admit that there is a place for deduplication as well as compression in reducing the footprint of customer data.  However, based on what I’ve seen in my career as an IT professional, and with my customers in my current role at EMC, there are more use cases for compression than there are for deduplication when it comes to primary data, whether SAN or NAS.  Either way, if I was using a new technology for the first time on a particular data set, whether compression or deduplication, I would definitely want a backout plan in case the drawbacks outweight the benefits.
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Unified of the Beholder???

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Apart from “The Cloud”, “Unified Storage” is the other big buzzword in the storage industry of late.  But what exactly is Unified Storage?

Mirriam-Webster defines unify as “to make into a unit or coherent whole“

So how does this apply to storage systems?  If you look at marketing messages by EMC, NetApp, and other vendors you’ll find that they all use the term in different ways in order to fit nicely with the products they have.  Based on what I see, there are generally two different approaches.

Single HW/SW Stack Approach:

Some vendors want you to believe that the only way it can be called Unified Storage is if the same physical box and software stack provides all protocols and features, even if management of the single system is not perfectly cohesive.

NetApp’s FAS storage systems are an example of this strategy.  A single filer provides all services whether SAN or NAS, IP or FiberChannel.  However, a single HA cluster is actually managed as two separate systems, each cluster node is managed independently using independent FilerView instances and there are separate tools (NetApp System Manager, Operations Manager, Provisioning Manager, Protection Manager) that can bring all of the filer heads into one view.  Disks are captive to a specific filer head in a cluster and moving disks and/or volumes between filer heads is not seamless.

Single Point of Management Approach:

Others approach it more holistically and figure that as long as the customer manages it as a single system, it qualifies as “Unified”, even if there may be disparate hardware and software components providing the different services.  After all, once it’s installed you don’t really go in the datacenter to physically look at the hardware very often.

EMC’s Unified Storage (which is a combination of Celerra NAS and Clariion Block storage systems) is an example of this.  In a best-of-breed approach, EMC allows the Clariion backend to do what it does best, block storage via FC or IP, while the Celerra, which is purpose built for NAS, provides CIFS/NFS services while leveraging the disk capacity, processors, cache, and other features of the Clariion as a kind of offload engine.  Regardless of which services you use, all parts of the solution are managed from a single Unisphere instance, including other Clariions and/or Celerras in the environment.  Unisphere launches from any Clariion or Celerra management port, and regardless of which device you launch it from, all systems are manageable together.

Which approach is better?

I see advantages and disadvantages to both approaches, as a former admin of both NetApp and EMC storage, I feel that while NetApp’s hardware and software stack is unified, their management stack is decidedly un-unified.  EMC’s Unified storage is physically “integrated” to work together as a system, but the unifying feature is the management infrastructure built-in with Unisphere.

There are other advantages to EMCs approach as well.  For example, if a particular workload seems to hammer the CPUs on the NAS but the backend is not a bottleneck, more Celerra datamovers can be added to take advantage of the same backend disks and improve front end performance.  Likewise, the backend can be augmented as needed to improve performance, increase capacity, etc without having to scale up the front end NAS head.  With the NetApp approach, if your CPU or cache is stressed, you need to deploy more FAS systems (in pairs for HA) along with any required disks for that new system to store data.

Both approaches work, and both have their merits, but what do customers really want?

In my opinion, most customers don’t really care *how* the hardware works, so long as it DOES WORK, and is easy to manage.  In the grand scheme of things, if I, as an admin, can provision, replicate, snapshot, and clone storage across my entire environment, regardless of protocol,  from a “single pane of glass”, that is a strong positive.

EMC Unisphere makes it easy to do just that and it launches right from the array with no separate installation or servers required.  Unisphere can authenticate against Active Directory or LDAP and has role-based-administration built in.  And since Unisphere launches from any Clariion Storage processor or Celerra Control Station, there’s no single point of failure for storage management either.

So what do you think customers want?  If you are a customer, what do YOU want?

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EMC Unified: Guaranteed Efficiency with Better Application Availability

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(Warning: This is a long post…)

You have a critical application that you can’t afford to lose:

So you want to replicate your critical applications because they are, well, critical.   And you are looking at the top midrange storage vendors for a solution.  NetApp touts awesome efficiency, awesome snapshots, etc while EMC is throwing considerable weight behind it’s 20% Efficiency Guarantee.  While EMC guarantees to be 20% more efficient in any unified storage solution, there is perhaps no better scenario than a replication solution to prove it.

I’m going to describe a real-world scenario using Microsoft Exchange as the example application and show why the EMC Unified platform requires less storage, and less WAN bandwidth for replication, while maintaining the same or better application availability vs. a NetApp FAS solution.  The example will use a single Microsoft Exchange 2007 SP2 server with ten 100GB mail databases connected via FibreChannel to the storage array.  A second storage array exists in a remote site connected via IP to the primary site and a standby Exchange server is attached to that array.

Basic Assumptions:

  • 100GB per database, 1 database per storage group, 1 storage group per LUN, 130GB LUNs
  • 50GB Log LUNs, ensure enough space for extra log creation during maintenance, etc
  • 10% change rate per day average
  • Nightly backup truncates logs as required
  • Best Practices followed by all vendors
  • 1500 users (Heavy Users 0.4IOPS), 10% of users leverage Blackberry (BES Server = 4X IOPS per user)
  • Approximate IOPS requirement for Exchange: 780IOPS for this server.
  • EMC Solution: 2 x EMC Unified Storage systems with SnapView/SANCopy and Replication Manager
  • NetApp Solution: 2 x NetApp FAS Storage systems with SnapMirror and SnapManager for Exchange
  • RPO: 4 hours (remote site replication update frequency)

Based on those assumptions we have 10 x 130GB DB LUNs and 10 x 50GB Log LUNs and we need approximately 780 host IOPS 50/50 read/write from the backend storage array.

Disk IOPS calculation: (50/50 read/write)

  • RAID10, 780 host IOPS translates to 1170 disk IOPS (r+w*2)
  • RAID5, 780 host IOPS translates to 1950 disk IOPS (r+w*4)
  • RAIDDP is essentially RAID6 so we have about 2730 disk IOPS (r + w*6)

Note: NetApp can create sequential stripes on writes to improve write performance for RAIDDP but that advantage drops significantly as the volumes fill up and free space becomes fragmented which is extremely likely to happen after a few months or less of activity.

Assuming 15K FiberChannel drives can make 180 IOPS with reasonable latencies for a database we’d need:

  • RAID10, Database 6.5 disks (round up to 8), using 450GB 15K drives =  1.7TB usable (1 x 4+4)
  • RAID5, 10.8 disks for RAID5 (round up to 12), using 300GB 15K drives = 2.8TB usable (2 x 5+1)
  • RAID6/DP, 15.1 disks for RAID6 (round up to 16), using 300GB 15K drives = 3.9TB usable (1 x 14+2)

Log writes are highly cachable so we generally need fewer disks; for both the RAID10 and RAID5 EMC options we’ll use a single RAID1 1+1 raid group with 2 x 600GB 15K drives.  Since we can’t do RAID1 or RAID10 on NetApp we’ll have to use at least 3 disks (1 data and 2 parity) for the 500GB worth of Log LUNs but we’ll actually need more than that.

Picking a RAID Configuration and Sizing for snapshots:

For EMC, the RAID10 solution uses fewer disks and provides the most appropriate amount of disk space for LUNs vs. the RAID5 solution.  With the NetApp solution there really isn’t another alternative so we’ll stick with the 16 disk RAID-DP config.  We have loads of free space but we need some of that for snapshots which we’ll see next.  We also need to allocate more space to the Log disks for those snapshots.

Since we expect about 10% change per day in the databases (about 10GB per database) we’ll double that to be safe and plan for 20GB of changes per day per LUN (DB and Log).

NetApp arrays store snapshot data in the same volume (FlexVol) as the application data/LUN so you need to size the FlexVol’s and Aggregates appropriately.  We need 200GB for the DB LUNs and 200GB for the Log LUNs to cover our daily change rate but we’re doubling that to 400GB each to cover our 2 day contingency.  In the case of the DB LUNs the aggregate has more than enough space for the 400GB of snapshot data we are planning for but we need to add 400GB to the Log aggregate as well so we need 4 x 600GB 15K drives to cover the Exchange logs and snapshot data.

EMC Unified arrays store snapshot data for all LUNs in centralized location called the Reserve LUN Pool or RLP.  The RLP actually consists of a number of LUNs that can be used and released as needed by snapshot operations occurring across the entire array.  The RLP LUNs can be created on any number of disks, using any RAID type to handle various IO loads and sizing an RLP is based on the total change rate of all simultaneously active snapshots across the array.  Since we need 400GB of space in the Reserve LUN Pool for one day of changes, we’ll again be safe by doubling that to 800GB which we’ll provide with 6 dedicated 300GB 15K drives in RAID10.

At this point we have 20 disks on the NetApp array and 16 disks on the EMC array.  We have loads of free space in the primary database aggregate on the NetApp but we can’t use that free space because it’s sized for the IOPS workload we expect from the Exchange server.

In order to replicate this data to an alternate site, we’ll configure the appropriate tools.

EMC:

  1. Install Replication Manager on a server and deploy an agent to each Exchange server
  2. Configure SANCopy connectivity between the two arrays over the IP ports built-in to each array
  3. In Replication Manager, Configure a job that quiesces Exchange, then uses SANCopy to incrementally update a copy of the database and log LUNs on the remote array and schedule for every 4 hours using RM’s built in scheduler.

NetApp:

  1. Install SnapManager for Exchange on each Exchange server
  2. Configure SnapMirror connectivity betweeen the two arrays over the IP ports built-in to each array
  3. In SnapManager, Configure a backup job that quiesces Exchange and takes a Snapshot of the Exchange DBs and Logs, then starts a SnapMirror session to replicate the updated FlexVol (including the snapshot) to the remote array.  Configure a schedule in Windows Task Manager to run the backup job every 4 hours.

Both the EMC and NetApp solutions run on schedule, create remote copies, and everything runs fine, until...

Tuesday night during the weekly maintenance window, the Exchange admins decide to migrate half of the users from DB1, to DB2 and DB3 and half of the users from DB4, to DB5 and DB6.  About 80GB of data is moved (25GB to each of the target DBs.)  The transactions logs on DB1 and DB4 jump to almost 50GB, 35GB each on DB2, DB3, DB5, and DB6.

On the NetApp array, the 50GB log LUNs already have about 10GB of snapshot data stored and as the migration is happening, new snapshot data is tracked on all 6 of the affected DB and Log LUNs.  The 25GB of new data plus the 10GB of existing data exceeds the 20GB of free space in the FlexVol that each LUN is contained in and guess what…  Exchange chokes because it can no longer write to the LUNs.

There are workarounds: First, you enable automatic volume expansion for the FlexVols and automatic Snapshot deletion as a secondary fallback.  In the above scenario, the 6 affected FlexVols autoextend to approximately 100GB each equaling 300GB of snapshot data for those 6 LUNs and another 40GB for the remaining 4 LUNs.  There is only 60GB free in the aggregate for any additional snapshot data across all 10 LUNs.  Now, SnapMirror struggles to update the 1200GB of new data (application data + snapshot data) across the WAN link and as it falls behind more data changes on the production LUNs increasing the amount of snapshot data and the aggregate runs out of space.  By default, SnapMirror snapshots are not included in the “automatically delete snapshots” option so Exchange goes down.  You can set a flag to allow SnapMirror owned snapshots to be automatically deleted but then you have to resync the databases from scratch.  In order to prevent this problem from ever occurring, you need to size the aggregate to handle >100% change meaning more disks.

Consider how the EMC array handles this same scenario using SANCopy.  The same changes occur to the databases and approximately 600GB of data is changed across 12 LUNs (6 DB and 6 Log).  When the Replication Manager job starts, SANCopy takes a new snapshot of all of the blocks that just changed for purposes of the current update and begins to copy those changed blocks across the WAN.

EMC Advantages:

  • SANCopy/Inc is not tracking the changes that occur AS they occur, only while an update is in process so the Reserve LUN Pool is actually empty before the update job starts.  If you want additional snapshots on top of the ones used for replication, that will increase the amount of data in the Reserve LUN Pool for tracking changes, but snapshots are created on both arrays independently and the snapshot data is NOT replicated.  This nuance allows you to have different snapshot schedules in production vs. disaster recovery for example.
  • Because SANCopy/Inc only replicates the blocks that have changed on the production LUNs, NOT the snapshot data, it copies only half of the data across the WAN vs SnapMirror which reduces the time out of sync.  This translates to lower WAN utilization AND a better RPO.
  • IF an update was occurring when the maintenance took place, the amount of data put in the Reserve LUN pool would be approximately 600GB (leaving 200GB free for more changed data).  More efficient use of the Snapshot pool and more flexibility.
  • IF the Reserve LUN Pool ran out of space, the SANCopy update would fail but the production LUNs ARE NEVER AFFECTED.  Higher availability for the critical application that you devoted time and money to replicate.
  • Less spinning disk on the EMC array vs. the NetApp.

EMC has several replication products available that each act differently.  I used SANCopy because, combined with Replication Manager, it provides similar functionality to NetApp SnapMirror and SnapManager.  MirrorView/Async has the same advantages as SANCopy/Incremental in these scenarios and can replicate Exchange, SQL, and other applications without any host involvement.

Higher Application availability, lower WAN Utilization , Better RPO, Fewer Spinning Disks, without even leveraging advanced features for even better efficiency and performance.

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Why pNFS can be a big deal even if NFS4.1 isn’t…

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It’s been a little while since I’ve posted, mostly due to my life being turned on it’s rear after our first child was born 8 weeks ago.  As things start to settle into a rhythm (as much as is possible) I’ve been back online more, reading blogs, following Twitter, and working with customers regularly.  As some of you may know, EMC announced support for pNFS in Celerra with the release of DART 6.x and there have been several recent posts about the technology which piqued my interest a little.

The other bloggers have done a good job of describing what pNFS is and what is new in NFS4.1 itself so I won’t repeat all of that.  I want to focus specifically on pNFS and why it IS a big deal.

Prior to my coming to work for EMC, I worked in internal IT at company that deals with large binary files in support of product development, as well as video editing for marketing purposes.  I had a chance to evaluate, implement, and support multiple clustered file system technologies.  The first was for an HD video editing solution using Mac’s and we followed the likely path of implementing Apple’s XSAN solution which you may know is an OEM’d version of Quantum(ADIC) StorNext.  StorNext allows you to create large filesystems across many disks and access them as local disk on many clients.  File Open, Close, byte-range locking, etc are handled by MetaData Controllers (MDCs) across an IP network while the actual heavy lifting of read/write IO is done over FibreChannel from the clients to the storage directly.  All the shared filesystem benefits of NAS with the performance benefits of SAN.

The second project was specifically targeted at moving large files (4+GB each) through a workflow across many computers as quickly as possible so we could ship products.  Faster processing of the workflow translated to more completed projects per person/per day which meant better margins and keeping our partners and customers happy.  The workflow was already established, using Windows based computers and a file server.  The file server was running out of steam and the amount of data being stored at any given time had increased from 500GB to 8TB over the past 12 months.  We needed a simple way to increase the performance of the file server and also allow for better scalability.  Working with our local EMC SE, we tested and deployed MPFSi using a Celerra NS40 with integrated storage.

MPFS has been around a long time (also known as High Road) and works with Windows and various *nix based platforms.  It is similar to XSAN/StorNext in that open/close/locking activity is handled over IP by the metadata controller (the Celerra datamover in the case of MPFS) while the read/write IO is handled over block storage technology (MPFS supports FibreChannel and iSCSI connectivity to storage).  The advantage of MPFS over many other solutions is that the metadata controller and storage are all built-in to the EMC Celerra storage device and you don’t have to deploy any other servers.

In our case we chose iSCSI due to the cost of FC (switches and HBAs) and used the GigE ports on the Celerra’s CX3 backend for block connectivity.  In testing we showed that CIFS alone provided approximately 240mbps of throughput over GigE connections while enabling MPFSi netted about 750mbps, even if we used the same NIC on the client.  So we tripled throughput over the same LAN by installing a software client.  Had we gone the extra mile to deploy FibreChannel for the block IO we would have seen much higher throughput.

Even better, the use of MPFS did not preclude the use of NDMP for backup to tape directly from the Celerra, accelerating backup many times over the old fileserver.  For clients that did not have MPFS software installed, they accessed the same files over traditional CIFS with no problems.  Another side benefit of MPFS over traditional CIFS, is that the block I/O stack is much more efficient than the NAS I/O stack so even with increased throughput, CPU utilization is lower on the client returning cycles to the application which is doing work for your business.

There are many clustered file system / clustered NAS solutions on the market from a variety of vendors (StorNext, MPFS, GFS, Polyserve, etc) and most of these products are trying to solve the same basic problems of storing more data and increasing performance.  The problem is they are all proprietary and because of that you end up with multiple solutions deployed in the same company.  In our case we couldn’t use MPFS for the video editing solution because EMC has not provided a client for Mac OSX.  And this is where pNFS really becomes attractive.  Storage vendors and operating system vendors alike will be upgrading the already ubiquitous NFS stack in their code to support NFS4.1 and pNFS.  And that support means that I could deploy an EMC Celerra MPFS like solution using the same Celerra based storage, with no extra servers, and no special client software, just the native NFS client in my operating system of choice.  Perhaps Apple will include a pNFS capable client in a future version of Mac OSX.

If you look at the pNFS standard you’ll see that it supports the use of not only block storage, but object and file based storage as well.  So as we build out larger and larger environments and private clouds start to expand into public clouds you could tier your pNFS data across FiberChannel storage, object storage (think Atmos on premises), as well as out to a service provider cloud (ie: AT&T Synaptic).  Now you’ve dramatically increased performance for the data that needs it, saved money storing the data that you need to keep long term, and geographically dispersed the data that needs to be close to users, with a single protocol supported by most of the industry and a single point of management.

Personally I think pNFS could kill off proprietary solutions over the long run unless they include support for it in their products.

This is just my opinion of course…

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Simplify Storage Management Today, Risk Free, and Free of Charge

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While my peers have been blogging about the new CLARiiON and Celerra releases, both of which provide significant enhancements to the EMC CX4-based Unified platforms you already own, I thought I’d shift gears just a tad…

What if you are a Clariion CX/CX3 customer, or a CX4 customer who isn’t ready to upgrade to the newly released FLARE30 code, but want to simplify management of your storage environment, get better reporting, dashboards, wizards, etc.  Well, you are in luck.

Just as with previous versions of Navisphere and FLARE, EMC offers off-array versions of Clariion management agents, servers, and GUIs.  As of yesterday, that includes off-array versions of Unisphere.  If you are a current customer of Clariion, you can login to PowerLink and download the Unisphere off-array software and build a management station.  After installation, you can manage your existing Clariion CX/CX3/CX4 hardware without upgrading the FLARE code.  As you upgrade your CX4 systems to FLARE30, new features will be enabled in Unisphere, and as you upgrade your Celerra NS systems to DART6, they can be added to the Clariion management domain and managed from the very same Unisphere instance.  How’s that for easy and convenient?

But what do you get by using Unisphere to manage your non-FLARE30 systems?  Unfortunately, you won’t be able to take advantage of FASTCache, FAST, Compression, and other features that are only available in FLARE 30, but there are some advantages..

First and foremost, Unisphere completely dumps the Navisphere tree-based management view and replaces it with end-result based tasks.  So instead of creating several objects to provision raid groups and LUNs, then present to a host, you just run the “Allocate” wizard and select the array, disks/raid group/pool, LUN size, hosts, etc and commit.

Second, upon launching Unisphere and logging in, you are immediately presented with dashboard views showing the amount of used/available storage, and active alerts, all customizable, so you can see the state of your entire CLARiiON storage environment “at-a-glance”.

To install Unisphere today, login to Powerlink, browse to “Support > Software Downloads and Licensing > Downloads T-Z > Unisphere Server Software” and download “EMC Unisphere Server” and “EMC Unisphere Client”.  Install them both to your Windows system and fire it up.  If you have Navisphere off-array software already installed, Unisphere will upgrade the existing installation for you.  You will also want to download and install Unisphere Service Manager (USM), also from Powerlink at “Support > Software Downloads and Licensing > Downloads T-Z > Unisphere Service Manager (USM).”  USM will provide various support and service related tools including active technical advisories for your storage arrays.

Begin using Unisphere today and you get some immediate benefits, plus you will be ready to take advantage of new features enabled with FLARE30 (FAST, FASTCache, Compression, etc) as well as managing NAS across all of your Celerra systems once they are upgraded to DART 6.  As a bonus, you’ll have a chance to get familiar with Unisphere before a future FLARE upgrade or new EMC Unified purchase forces you to learn it.

And did I mention you don’t have to buy anything or introduce risk with a firmware upgrade?

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Lies, Damn Lies, and Marketing…

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Yesterday, In his blog posted entitled “Myth Busting: Storage Guarantees“, Vaughn Stewart from NetApp blogged about the EMC 20% Guarantee and posted a chart of storage efficiency features from EMC and NetApp platforms to illustrate his point.  Chuck Hollis from EMC called it “chartsmithing” in comment but didn’t elaborate specifically on the charts deficiencies.  Well allow me to take that ball…

As presented, Vaughn’s chart (below) is technically factual (with one exception which I’ll note), but it plays on the human emotion of Good vs Bad (Green vs Red) by attempting to show more Red on EMC products than there should be.

The first and biggest problem is the chart compares EMC Symmetrix and EMC Clariion dedicated-block storage arrays with NetApp FAS, EMC Celerra, and NetApp vSeries which are all Unified storage systems or gateways.  Rather than put n/a or leave the field blank for NAS features on the block-only arrays, the chart shows a resounding and red NO, leading the reader to assume that the feature should be there but somehow EMC left it out.

As far as keeping things factual, some of the EMC and NetApp features in this chart are not necessarily shipping today (very soon though, and since it affects both vendors I’ll allow it here).  And I must make a correction with respect to EMC Symmetrix and Space Reclamation, which IS available on Symm today.

I’ve taken the liberty of massaging Vaughn’s chart to provide a more balanced view of the feature comparison.  I’ve also added EMC Celerra gateway on Symmetrix to the comparison as well as an additional data point which I felt was important to include.

I’ve included some footnotes in the chart to explain some of the results but I’ll explain a little here as well.

1.) I removed the block only EMC configuration devices because the NetApp devices in the comparison are Unified systems.

2.) I removed the SAN data row for Single Instance storage because Single Instance (identical file) data reduction technology is inherently NAS related.

3.) Zero Space Reclamation is a feature available in Symmetrix storage.  In Clariion, the Compression feature can provide a similar result since zero pages are compressible.

I left the 3 different data reduction techniques as individually listed even though the goal of all of them is to save disk space.  Depending on the data types, each method has strengths and weaknesses.

One question, if a bug in OnTap causes a vSeries to lose access to the disk on a Symmetrix during an online Enginuity upgrade, who do you call?  How would you know ahead of time if EMC hasn’t validated vSeries on Symmetrix like EMC does with many other operating systems/hosts/applications in eLab?

The goal if my post here really is to show how the same data can be presented in different ways to give readers a different impression.  I won’t get into too much as far as technical differences between the products, like how comparing FAS to Symmetrix is like comparing a box truck to a freight train, or how fronting an N+1 loosely coupled clustered, global cached, high-end storage array with a midrange dual-controller gateway for block data might not be in a customer’s best interest.

What do you think?

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Resiliency vs Redundancy: Using VPLEX for SQL HA

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A little history on my philosophy around high-availability

Around the year 2000, when I was working in network operations for a large wireless telco, a very senior network architect explained to me the company’s philosophy on building high availability solutions into the network.  The phrase I remember from that conversation was “we don’t build redundant networks, we build resilient networks..” The difference is that while redundant networks failover to secondary paths to resume traffic, resilient networks don’t go down at all.  This concept has stuck with me ever since and I tend to tackle high-availability problems of all kinds with this idea in mind.  It’s frankly been very difficult to build solutions that are resilient across the entire stack, mostly because infrastructure technology hasn’t quite gotten there yet.

Things may have changed…

I recently had a meeting with a customer to discuss local high availability for SQL.  This customer has a very large multi-node clustered SQL environment (hundreds of TBs of data, hundreds of databases, hundreds of instances, many clusters, many nodes per cluster) and has been testing SQL database mirroring as an alternative to traditional Windows Failover Clustering.  The focus of the meeting wound up focused primarily on leveraging VPLEX as an alternative to SQL mirroring, and the reasons for that decision suddenly reminded me of the Resiliency vs Redundancy discussion I had years ago.  A VPLEX solution potentially solves the same problem as DB mirroring, does it with less complexity, and less risk.

VPLEX Local as a Resilient HA solution

One of the many features of VPLEX is it’s ability to mirror data across multiple storage arrays and present that mirror as a single LUN to the host.  For customers already running large multi-node MSCS clusters, the LUN appears just like any normal storage LUN and Windows/SQL treat the LUN normally.  There are several reasons VPLEX should be considered as an alternative to database mirroring. (much of this applies to Exchange CCR as well)

VPLEX hardware is inherently Resilient.  A VPLEX cluster is an N+1 cluster of loosely coupled nodes, cooperating with each other, but not depending on each other.  Hosts can access any of the hosted data, through any of the ports, on any of the cluster nodes.  If a node fails for any reason, the remaining nodes continue serving IO for any data.  Except for a dead path on the host side (managed by PowerPath or MPIO), there is no failover process, and no cache mirroring to worry about.  The potential performance impact of a failure is equal to 1, divided by the quantity of that component in the cluster. (128 x 8gbe ports across 8 director nodes for a large VPLEX Local cluster)

In addition, because VPLEX utilizes a write-through cache, there is never any dirty cache data (data in cache that has not been committed to disk) in a VPLEX system.  A power outage or VPLEX hardware failure does not put data at risk.

Other Advantages of using VPLEX over SQL Database Mirroring

Improved Performance:

  • Compared with SQL Database mirroring, VPLEX mirroring has significantly less impact on transaction performance for writes and can improve transaction performance in some cases due to the large read cache in the VPLEX directors. (Note: I am comparing to DB Mirroring in Full-Safety mode since the customer’s requirement was a zero-data-loss solution.)

Non-Disruptive Storage Failover:

  • In the event of a storage failure, SQL Mirroring must perform a cluster node failover which takes a few seconds at best, possibly disrupting applications.  VPLEX provides completely non-disruptive failover when a storage failure occurs.  (A server hardware failure still triggers a node failover as it would in any other failover clustering scenario.)

Less Management Overhead:

  • From a management perspective, using VPLEX instead of SQL Database mirroring gives the SQL DBAs fewer SQL instances and fewer moving parts to manage on a daily basis.  The storage team just presents a mirrored LUN from VPLEX to the cluster and it’s business as usual for the DBAs.
  • VPLEX also allows the storage team to non-disruptively migrate data between storage arrays behind VPLEX to balance load, perform hardware refreshes, resolve capacity problems.  VPLEX performs the migration at the direction of the storage admins.

Reduced Risk:

  • Reducing management complexity also reduces risk.  With a high number of database instances and db mirrors involved in a large environment like this one, the chance of one of those mirrors having a problem, or being configured incorrectly, is increased.  DBAs can rely on VPLEX mirroring all of the data, 24x7x365, even when host maintenance is being performed.

Reduced Cost:

  • When compared with the SQL Database Mirroring solution, the VPLEX solution reduced the number of physical servers needed in this environment, reducing cost enough to more than offset the cost of VPLEX itself.  Combined with reductions in soft costs, like reduced DBA management overhead, VPLEX will actually save them quite a bit of money, and increased uptime during storage refresh and maintenance will increase revenues in this case as well.

A Distributed Future:

  • Next year, when a second datacenter is online nearby, the first VPLEX Local cluster can be connected to another VPLEX cluster in the new datacenter.  Then the SQL cluster nodes and data can be distributed across both datacenters, providing protection from entire datacenter outages, or solving space constraints with no changes to the application or servers, and no downtime.

I wonder how many other customers would like to build more resilient infrastructures?

If you combine a VPLEX solution with a true cluster file system and an active-active database engine (ie: Oracle RAC), you can eliminate the disruption caused by server hardware failures.  It’s just a matter of time now until the entire stack can be designed for true resiliency with very little management overhead.  I can’t wait to see what happens.

The following EMC White Paper has a lot of good information about using VPLEX in this same context:

Workload Resiliency with EMC VPLEX

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While EMC users benefit from Replication Manager, NetApp users NEED SnapManager

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This is a follow up to my recent post NetApp and EMC: Replication Management Tools Comparison, in which I discussed the differences between EMC Replication Manager and NetApp SnapManager.

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As a former customer of both NetApp and EMC, and now as an employee of EMC, I noticed a big difference between NetApp and EMC as far as marketing their replication management tools. As a customer, EMC talked about Replication Manager several times and we purchased it and deployed it. NetApp made SnapManager a very central part of their sales campaign, sometimes skipping any discussion of the underlying storage in favor of showing off SnapManager functionality. This is an extremely effective sales technique and NetApp sales teams are so good at this that many people don’t even realize that other vendors have similar, and in my opinion EMC has better, functionality.  One of the reasons for this difference in marketing strategy is that NetApp users NEED SnapManager, while EMC users do not always need Replication Manager.

The reason why is both simple and complex…

EMC storage arrays (Clariion, Symmetrix, RecoverPoint, Invista) all have one technology in common that NetApp Filers do not–Consistency Groups. A consistency group allows the storage system to take a snapshot of multiple LUNs simultaneously, so simultaneous in fact that all of the snapshots are at the exact same point in time down to the individual write. This means that, without taking any applications offline and without any orchestration software, EMC storage arrays can create crash-consistent copies of nearly any kind of data at any time.

The EMC Whitepaper “EMC CLARiiON Database Storage Solutions: Oracle 10g/11g with CLARiiON Storage Replication Consistency” downloadable from EMC’s website has the following explanation of consistency groups in general…

“…Consistent replication operates on multiple LUNs as a set such that if the replication action fails for one member in the set, replication for all other members of the set are canceled or stopped.  Thus the contents of all replicated LUNs in the set are guaranteed to be identical point-in-time replicas of their source and dependent-write consistency is maintained…”

“…With consistent replication, the database does not have to be shut down or put into “hot backup mode.”  Replicates created with SnapView or MV/S (or MV/A, Timefinder, SRDF, Recoverpoint, etc) consistency operations, without first quiescing or halting the application, are restartable point-in-time replicas of the production data and guaranteed to be dependent-write consistent.”

Consistency is important for any application that is writing to multiple LUNs at the same time such as SQL database and log volumes. SnapManager and Replication Manager actually prepare the application by quiescing the database during the snapshot creation process. This process creates “application-consistent” copies which are technically better for recovery compared with “storage-consistent” copies (also known as crash-consistent copies).

So, while I will acknowledge that quiescing the database during a snapshot/replication operation provides the best possible recovery image, that may not be realistic in some scenarios.  The first issue is that the actual operation of quiescing, snapping, checking the image, then pushing an update to a remote storage array takes some time.  Depending on the size of the dataset, this operation can take from several minutes to several hours to complete.  If you have a Recovery Point Objective (RPO) of 5 minutes or less, using either of these tools is pretty much a non-starter.

Another issue is one of application support.  EMC Replication Manager and NetApp SnapManager have very wide support for the most popular operating systems, filesystems, databases, and applications, they certainly don’t support every application.  A very simple example is a Novell Netware file server with a NSS pool/volume spanning multiple LUNs.  Neither NetApp nor EMC have support for Novell Netware in their replication management tools.  While you can certainly replicate all of the LUNs with NetApp SnapManager, SnapManager has no consistency technology built-in to keep the LUNs write-order consistent.  The secondary copy will appear completely corrupt to the Netware server if a recovery is attempted.  Through the use of consistency groups with MirrorView/Async, the replication of each LUN is tracked as a group and all of the LUNs are write-order consistent with each other, keeping the filesystem itself consistent.  You would need to have either array-level consistency technology, or support for Netware in the replication management tool in order to replication such a server..  Unfortunately, NetApp provides neither.

You may have complex applications that consist of Oracle and SQL databases, NTFS filesystems, and application servers running as VMs.  Using array-based consistency groups, you can replicate all of these components simultaneously and keep them all consistent with each other.  This way you won’t have transactions that normally affect two databases end up missing in one of the two after a recovery operation, even if those databases are different technologies (Oracle and MySQL, or PostgreSQL for example).

EMC Storage arrays provide consistency group technology for Snapshots and Replication in Clariion and Symmetrix storage arrays.  In fact, with Symmetrix, consistency groups can span multiple arrays without any host software.  By comparison, NetApp Filers do not have consistency group technology in the array.  Snapshots are taken (for local replicas and for SnapMirror) at the FlexVolume level.  Two FlexVolumes cannot be snapped consistently with each other without SnapManager.

There are a couple workarounds for NetApp users–you can snapshot an aggregate, but that is not recommended by NetApp for most customers, or you can put multiple LUNs in the same FlexVol, but that still limits you to 16TB of data including snapshot reserve space, and both options violate best practices for database designs of keeping data and logs in separate spindles for recovery.  Even with these workarounds, you cannot gain LUN consistency across the two controllers in an HA Filer pair, something the CLARiiON does natively, and can help for load balancing IO across the storage processors.

In general, I recommend that EMC customers use EMC Replication Manager and NetApp customers use SnapManager for the applications that are supported, and for most scenarios.  But when RPO’s are short, or the environment falls outside the support matrix for those tools, consistency groups become the best or only option.

Incidentally, with EMC RecoverPoint, you get the best of both worlds.  CDP or near-CDP replication of data using consistency groups for zero or near-zero RPOs plus application-consistent bookmarks made anytime the database is quiesced.  Recovery is done from the up-to-the-second version of the data, but if that data is not good for any reason, you can roll back to another point in time, including a point-in-time when the database was quiesced (a bookmark).

So, while EMC has, in Replication Manager, an equivalent offering to NetApp’s SnapManager, EMC customers are not required to use it, and in some cases they can achieve better results using array-based consistency technologies.

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