Richard J Anderson

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?