Deploying Microsoft Exchange within an organization is a decision not to be made lightly. With so many websites offering Exchange hosting, its tempting to pass the torch to an outside entity. Of course that temptation may quickly subside depending on the cost analysis of using an Exchange hosting company versus running your own Exchange server.
When planning for Exchange 2007, you need to decide early on what server roles you require, and how many servers you will need to accomplish this. Exchange 2007 is broken up into the Mailbox, Client Access, Hub Transport, Edge Transport, and Unified Messaging roles.
You can run all of these roles on a single server, or you can spread them out with an Edge Transport server, a Client Access server, one for Unified Messaging (if you intend to use this functionality), and one server containing the Hub transport and Mailbox roles. The best approach is to figure out how many servers you are able to maintain in your current network infrastructure.
Keep in mind that when you are initially configuring the hardware for your Exchange 2007 environment, more hardware crammed into a server, is not always better. Exchange 2007 is 64-bit, will be running on Windows Server 64-bit, and makes excellent use of 64-bit processors. Because of this, you are not limited to the 4GB memory ceiling in the previous 32-bit Windows environment.
However, processors, specifically the number of cores, demand extra attention due to the specifics of what server roles you are using on what hardware. A Microsoft TechNet article (seen here) gives a break down of how many processor cores per server role, are recommended (not an absolute rule). For instance, the Mailbox role supports a minimum of a single processor core, but a maximum recommendation of twelve cores.
So you could have a server with a single processor, with a single core, which is not common for new hardware on today’s market; or you could run a server with six, dual-core processors. A practical choice would be a pair of quad-core processors, which could safely handle the processing requirements for the Mailbox role.
That said, what if you wanted to run multiple roles on one server? In this instance, your limitation, if you will, is the smallest amount of maximum recommended processor cores for a server role. For example, while the Mailbox role can utilize twelve cores, the Client Access role tops off at six. If you had the Client Access role running alongside the Mailbox role, a practice measure is to have two or three dual-core processors.
Setting aside the processor matter, we need to examine the server’s memory needs. A partner article to the previous TechNet post, gives the reader suggestions for the amount of memory needed for each server role. All server roles prefer a minimum of 2GB each, but again, this is the base requirement. Combining server roles asks for a minimum of 4GB of RAM.
The article covering the Exchange 2007 memory requirements (seen here) does a fair job of giving a technician the basic memory specifications, however, one will have to carefully examine their organization in order to fully calculate RAM usage. While there are statements, in the article, to effect of measuring email use against the amount of needed memory, be careful not to simply install the calculated result.
If your number of users is around 300 and your math leads you to 16GB of RAM, why not go with 20GB of RAM? The monetary difference is less than in years past, and having additional memory is an easy safety net to have in place prior to deployment.
In the realm of non-volatile storage, the hard drive space you will need starts with what you are currently using, plus the outlook for future usage. Since hard drives are continually lowering in cost, this is another instance where buying additional hardware is a good measure. There are some special considerations with Exchange 2007 when is comes to storage though.
As with the other hardware recommendations, Microsoft’s TechNet contains a posting (seen here) for the storage considerations with Exchange 2007. Among other matters, it points out four RAID types, and how each of them performs with Exchange 2007. This subject requires scrutiny on the part of the system administrators because they must decide if performance, storage capacity, or disk fault tolerance is the most important.
Keep in mind that the TechNet article appears to be leaning towards fair sized deployments of Exchange 2007. If you have a smaller system setup that supports 50 mailboxes, and the mailbox databases reside on a RAID 1 mirrored disk pair, you may not necessarily notice any performance difference than on a RAID 5 disk array. Of course you may want more redundancy than a simple pair of hard drives.
In addition to the RAID considerations and physical disk size, what about the mailbox sizes? Does your current email system have caps in place for individual mailboxes? Do you have a universal limit on all mailboxes or are the caps mitigated by employee position or job function?
Perhaps someone on a shop floor, that only receives production orders, can function fine on a mailbox cap of 500 MB. However, someone working in the marketing department may require a larger cap in order to track emails with design specification attachments.
With Exchange 2007, you have a greater availability of storage groups, than Exchange 2003. With the Enterprise edition of 2007, you can have up to 50 storage groups for each server. In practical administration terms, you could allocate one storage group for each individual department in a company, and manage the storage group, instead of individual mailboxes. Doing so could cut down on the time spent to size storage accordingly by focusing on consolidated groups rather than the hand count of each user’s mailbox.
So let’s wrap this up with a real world example.
One small manufacturing company, 100 mailboxes of varying sizes, no current mailbox cap (except for the Exchange 5.5, 16GB database limit), multiple Outlook PST files on varying end user computers, and an aging Exchange 5.5 server (A single 500 MHz Pentium 3 processor, 1GB of RAM, and a RAID 1 36GB hard drive pair).
Total storage required, 15GB (current Exchange 5.5 database mail store), plus 40GB worth of email in various PST files throughout the company. In this particular instance, the Postini service is already in place for perimeter email spam and virus protection, and it will be used in place of the Edge Transport server role.
Email server solution: New pair of servers with the assumption of other service running on them (DNS service, security software, defragmentation software service, and other monitoring utilities). The first server contains the Exchange 2007 Hub Transport and Mailbox server roles.
This server is configured with a pair of Pentium 4 Dual-Core processors (total of 4 cores), 16GB of RAM, and a pair of 72GB hard drives (for the operating system and Exchange 2007 log files, in RAID 1). The actual Exchange mailbox stores will be housed on a fiber attached storage array with a RAID 1/0 setup.
Four 146GB hard drives will provide the fault tolerance, performance, and space for the combination of the original email store plus the email unloaded from the PST files. The fiber attached storage array has four open bays for future hard disk expansion.
Three initial storage groups will be created within the Mailbox role, labeled as High, Medium, and Low. These are specifically named due to the nature of employee’s email usage. People using the least amount of email storage are placed in the Low storage group, the heaviest users in the High group, and everyone else falls in the Medium category.
The second server will be the Client Access server role piece. It is configured with a pair of Pentium 4, dual-core processors, 6GB of RAM, and a pair of 72GB hard drives in a RAID 1 configuration. Keeping the Client Access role separate lessens the processor load on the Mailbox server. This server will house additional log files from the Client Access role, as well as serving as a future connection point for Windows Mobile enabled devices.
Referenced Articles:
http://technet.microsoft.com/en-us/library/aa998874.aspx – Exchange 2007, Planning Processor Configurations
http://technet.microsoft.com/en-us/library/bb738124.aspx – Exchange 2007, Planning Memory Configurations
http://technet.microsoft.com/en-us/library/bb738146.aspx – Exchange 2007, Storage Technology
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