Joe has been posting a nice buyer’s guide about the features available on various SAN storage products. But it doesn’t really address the question of why move from direct attached storage (DAS) to a SAN. What benefits does a SAN bring to an organization?

To answer the question, we have to look at how storage is purchased and provisioned without SAN based storage.

Say you have an older File Server which currently has 500GB of data but can’t take any more drives.  Performance is fine but you decide you need to upgrade to a new server to add more capacity. You want the new server to have room to grow, so you spec out and order a server with 1TB of disk space. You also have Mail Server. It’s a pretty new server, but you recently merged with another company and the mail store size doubled overnight.  It needs storage and fast, but not a lot as you don’t anticipate the mail store growing so quickly in the future. You have 500GB of storage sitting on the new File Server, but you can’t use any of it to host the mail store.  So you order an external tray with just a couple drives and still end up with more storage than you need.  

Ten months later you look and see that file server data is growing rapidly and the free space is already gone.  You have an external tray attached the mail server, but you can’t use that to attach it to both servers. So you have to purchase a separate tray for the file server.

This example is over simplified, but it highlights three problems of direct attached storage:

·         Poor scalability

·         Poor Utilization

·         Silos of storage

Poor Scalability

It is not uncommon for an entire server to be replaced just to increase capacity. Not only is this expensive, but if the old server was performing fine you are buying additional resources (processing power and RAM) that you don’t really need. Adding external trays allows you to add large chunks of capacity, but what if you only need a bit more space. 

Poor Utilization

Data growth is dynamic which makes calculating your future needs difficult. The lack of flexibility in DAS discussed above and the fact that adding capacity frequently involves downtime or complete server migration leads organization to buy much more storage upfront than they need.  The result is servers with considerable amounts of unused storage.

Silos of storage

Because of the two problems above you end up with servers with spare capacity, but it is unavailable if another server needs it.  You have storage you’ve paid for but can’t use. Organizations respond in two ways, they either accept this inefficiency or start adding multiple services to servers that have space even if it violates best practices.  An example would be adding high usage file shares to your mail server.

How a SAN helps

A properly designed and deployed SAN addresses each of these problems.  SAN based storage is scalable, flexible, and allows storage to be shared between servers.  The end result can be better storage utilization meaning you only buy the storage you need and can easily add more as needed.  SAN based storage is also a critical element that enables organization to effectively utilize advanced technologies like clustering and virtualization.

Hopefully you now understand the benefits of SAN based storage and have decided it’s time to add it to your organization.  As you can tell by the number of features Joe has in his buying guide, there are many more options and decisions to make. Like any new technology deployment, good guidance can mean the difference between a successful deployment and failure. In future posts I’ll break down:

·         What is a SAN? Or more accurately what components make up a SAN?

·         How should a SAN be used and how should it not be used?  There are many ways to deploy a SAN can limit its utility and seem to be more expensive and troublesome than it works.