Microsoft's Recommendations for Exchange Storage Configurations aren't Wrong, They are Just Out of Date

No technology has become more ubiquitous or more critical to day-to-day business processes than email with Microsoft Exchange Server now arguably the email software that most businesses rely on. But even as Microsoft Exchange has become so widely adopted (65% of all organizations now use Exchange according to a recent report from Ferris Research) and the release of Exchange 2010 looming, information about how to optimally configure specific resources that Exchange uses still remains in short supply. Nowhere is this dearth of information more evident than in what new options are available to administrators as they look to configure and optimize the back end storage assigned to Exchange.

This is not to imply that Microsoft does not provide any guidance on how administrators should configure the storage that they allocate to Microsoft Exchange - Microsoft does do that. However the advice it dispenses are guidelines at best and it does not take into account new storage technologies that are now readily available to users. For instance, here is just one excerpt I pulled from the Microsoft Exchange Team's blog on how to configure, validate and monitor your Exchange 2007 storage:

"Mailbox Size/Mailbox Count... For example, if you have 4000 users on a server with a 250MB mailbox quota, then you need at least 1TB of disk space. Moreover, there are additional components which must be factored into the equation. If a hard limit is not set on the mailbox quota, it is difficult to estimate the how much capacity you will need."

On the surface, the recommendation seems pretty solid. But what that recommendation (and many of the others made in that blog) does not take into account is recent advances that have occurred in storage system technologies. This example of reserving 1 TB of storage for 4000 users so they have sufficient capacity for their mailboxes with 250 MB quota may not sound like a lot of storage but there are a number of problems with that recommendation:
 

• First, that blog entry was written in 2007, not 2009. In 2009, mailbox quotes are closer to 1 GB than 250 MB (which is confirmed by another post on Microsoft's website) so the capacity requirements for users are now fourfold of what they were just 2 years ago
• Second, only a fraction of the 4000 users (say 20%) are actually going to approach their 1 GB quota while the other 80% may only use a few hundred MBs of storage. Since an administrator may not know which 20% are going to need the 1 GB of storage, the administrator treats everyone the same and gives them 1 GB of storage. As a result, 2 - 3 TB of storage capacity is unutilized and wasted.
• Finally, 2 - 3 TBs of wasted storage may sound like a rounding error in today's era of 1 TB disk drives but most Exchange implementations require that the data is stripped across multiple high performance disk drives to meet Exchange performance and availability requirements. So the amount of disk storage space and corresponding cost required to deliver on just the user mailbox requirements for Exchange may far exceed the minimum 4 TB of useable capacity that this specific implementation of Exchange calls for.

A better approach to thinking about how to configure one's storage for Exchange is to think about the new technologies that have become more widely adopted since 2007 like thin provisioning or wide striping such as what 3PAR's InServ Storage models offer. These features can dramatically reduce storage requirements, improve performance and enable organizations to do faster backups and recoveries of their Exchange environments. In a forthcoming blog entry, I'll elaborate at how new storage features like what 3PAR supports should prompt organizations to rethink the layout of the back end for their Exchange storage deployments and what new best practices they should consider when deploying Exchange with this next generation of storage systems.