Exchange Server 2007 Requirements
To properly support Exchange 2007, you need to make sure the hardware you are using meets certain minimum requirements. This is certainly true if you are expecting Exchange 2007 to perform as expected and you expect to run in an environment supported by Microsoft. The hardware and software requirements are a bit more complex than they were for previous generations of Exchange.
Hardware Requirements
In the past, Microsoft has made recommendations for hardware based on the absolute minimums required to run Exchange Server. Now, however, the recommendations are much more practical for real-world deployments. The goal is optimal performance, and the recommendations are now made with consideration for supporting applications that often run in concert with Exchange Server, such as antivirus, anti-spam, archiving, management, monitoring, and reporting software.
Processors
The requirement for 64-bit processors is the first big change for Exchange 2007. The processor should be at least an 800MHz processor, though you will certainly benefit from processors faster than 2GHz or dual-core processors. The processor must be either an Intel Xeon or Intel Pentium x64 processor that supports the Intel Extended Memory 64 Technology (EM64 T) or an AMD Opteron or Athlon 64-bit processor that supports the AMD64 platform. The Intel Itanium IA64 processor family is not supported. Table 2.1 shows the processor recommendations from Microsoft for different Exchange Server 2007 roles.
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| Exchange 2007 Server Role | Minimum | Recommended | Recommended Maximum |
|---|---|---|---|
| Edge Transport | 1 × processor core | 2 × processor cores | 4 × processor cores |
| Hub Transport | 1 × processor core | 4 × processor cores | 4 × processor cores |
| Client Access | 1 × processor core | 4 × processor cores | 4 × processor cores |
| Unified Messaging | 1 × processor core | 4 × processor cores | 4 × processor cores |
| Mailbox | 1 × processor core | 4 × processor cores | 8 × processor cores |
| Multiple server roles (combinations of Hub Transport, Client Access, Unified Messaging, and Mailbox server roles) | 1 × processor core | 4 × processor cores | 4 × processor cores |
Open table as spreadsheet |
You may have noticed in Table 2.1 that for some server roles, the maximum number of processors or processor cores is less than the maximum that Windows can actually support. Most all multithreaded applications will reach a point of diminishing returns when more processors are added, so it may not be worth it to add the maximum number of processors that Windows supports.
In environments that scale past a few hundred mailboxes, certainly dual-or quad-processor systems will be put to good use. For organizations that deploy Exchange Server in a combination of roles to different physical machines, you will almost always benefit from a dual-processor or dual-core processor system.
Physical Memory
As we have mentioned previously, the advantage that Exchange 2007 really gets out of the 64-bit architecture is the ability to access more physical memory. Additional physical memory improves caching, reduces the disk I/O profile, and allows for the addition of more features.
Microsoft is recommending a minimum of 1GB of RAM in each Exchange 2007 server or 2GB for each server supporting the Mailbox server role. This will, of course, depend on the roles that the server is supporting. Table 2.2 shows the minimum recommended memory for each of the server roles.
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| Server Role | Minimum | Recommendation | Maximum |
|---|---|---|---|
| Mailbox | 2GB | 2GB base memory plus per mailbox calculation. | 32GB |
| Hub Transport | 1GB | 1GB per CPU core | 16GB |
| Client Access | 1GB | 1GB per CPU core | 4GB |
| Unified Messaging | 1GB | 1GB minimum plus 512MB for each additional CPU core | 4GB |
| Edge Transport | 1GB | 1GB per CPU core | 16GB |
| Multiple roles | 2GB | 4GB for combination Hub Transport, Client Access, and Unified Messaging plus the per-mailbox calculation | 8GB |
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Once you have calculated the minimum amount of RAM that you require for the server, if you are configuring a mailbox server, you will need to add some additional RAM for each mailbox. This will depend on your user community's estimated load profile. Table 2.3 shows the additional memory required based on the number of mailboxes supported.
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| User profile | Mailbox Memory Recommendation |
|---|---|
| Light | Add 2MB per mailbox |
| Average | Add 3.5MB per mailbox |
| Heavy | Add 5MB per mailbox |
|
| Tip | If you are curious what constitutes light, average, and heavy users, these are defined later in this chapter in Table 2.5. |
So for example, a server handling a Mailbox server role should have 2GB of memory plus the additional RAM per mailbox shown in Table 2.3. If the Mailbox server is supporting 1,000 mailboxes and it is estimated that 500 of the users are average (1.75GB of RAM) and 500 are heavy users (2.5GB of RAM), the server should have about 6.3GB of RAM. For good measure, we would recommend going with 8GB of RAM so that there is additional RAM just in case it is required. Seasoned administrators of previous versions of Exchange will immediately notice that restrictions on usable physical memory no longer apply to Exchange 2007.
Remember that these RAM estimates are just that, estimates. Additional factors may require more or less RAM (usually more) than the calculations and recommendations here. For example, antivirus and anti-spam software on Mailbox servers can place a significant burden on RAM.
An alternate way to size memory for Mailbox servers is to estimate the amount of RAM required based on the number of storage groups. This method is calculated to ensure that each storage group (and mailbox database) that is in use is allocated sufficient memory for database caching. Table 2.4 shows the minimum memory recommendations based on storage groups.
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| Number of Storage Groups | Minimum RAM Required |
|---|---|
| 1–4 | 2GB |
| 5–8 | 4GB |
| 9–12 | 6GB |
| 13–16 | 8GB |
| 17–20 | 10GB |
| 21–24 | 12GB |
| 25–28 | 14GB |
| 29–32 | 16GB |
| 33–36 | 18GB |
| 37–40 | 20GB |
| 41–44 | 22GB |
| 45–38 | 24GB |
| 49–50 | 26GB |
|
If you calculate two different minimum recommendations for RAM, we strongly encourage you to use the larger of the two calculations. Up to 32GB, Exchange 2007 Mailbox servers will always benefit from additional performance. Of course, 32GB of RAM may not be required on a Mailbox server that is supporting only 200 mailboxes, so approach RAM sizing with a certain cautious exuberance.
Optical Media
Exchange Server 2007 ships only on DVD media. Although installing from a network share does work, it is generally a good idea to ensure that your servers have DVD drives available rather than CD-ROM drives. If your servers do not have DVD drives, you can still copy the Exchange software across the network or install from a network share folder.
File System
The FAT and FAT32 file systems are not supported. All disks must be formatted using the NTFS file system.
Disk Space
Exchange Server 2007 is certainly not the first edition of Exchange for which administrators or designers have improperly sized the amount of available disk space. More than a few times, we have seen administrators scrambling for more disk space, adding additional hard drives, moving databases and transaction logs around, or begging the storage area network (SAN) administrator for more disk space. This is so important, in fact, that we are dedicating an entire section to this in Chapter 3, "Designing a New Exchange 2007 System."
For now, let's just leave the disk requirements at the utmost basics. We recommend that each system disk on an Exchange Server have at least 10GB of free disk space prior to the installation of Exchange 2007. The actual recommendation from Microsoft is 1.2GB disk space free and 200MB of free space on the system disk, but that is a bare minimum. The amount of disk space that each of the servers will actually require will depend on the server role, the number of users you support, mailbox limits, and leaving room to grow.
Operating System Requirements
There are a few requirements for the Windows Server operating system. For the release to manufacturing (RTM) version of Exchange 2007, the only version of Windows Server that can be used is the Windows Server 2003 x64 SP1 (or later) or Windows Server 2003 x64 R2 family. Windows 2003 with the Multilingual User Interface (MUI) pack can also be used.
Exchange 2007 can be installed on either the Standard Edition or Enterprise Edition of Windows Server 2003. Windows 2003 Enterprise Edition is required if you will be installing clustered mailbox servers.
At some point in the future, Microsoft will include support for Exchange 2007 to run on top of the new Windows Server operating system that is currently code-named Longhorn. This will be in the time frame of Exchange 2007 Service Pack 1. Do not try to install Exchange 2007 on Longhorn Server in production until you have specific instructions from Microsoft as to how to support it.
The following list includes other requirements for preparing the Windows server to run Exchange 2007:
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Install the Microsoft .NET Framework v2.0.
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Install the Windows PowerShell. The released version can be downloaded from http://preview.tinyurl.com/e5x2t.
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Install Microsoft Management Console 3.0. You can find more information and download links in Microsoft Knowledge Base article 907265, "MMC 3.0 update is available for Windows Server 2003 and for Windows XP."
| Note | Unlike with previous versions of Exchange, the Internet Information Server components Network News Transfer Protocol (NNTP) and Simple Mail Transfer Protocol (SMTP) should not be installed. |
All additional applications that you run on an Exchange 2007 server should be 64-bit applications. Although Windows x64 supports 32-bit applications in WOW64 emulation provided the applications' kernel mode components are 64-bit, it remains to be seen whether mixing and matching 32-bit and 64-bit applications on an Exchange 2007 server is a good idea. Many of us still remember poorly performing and unstable 16-bit Windows applications that adversely affected Windows NT 4.0, so this may potentially be true with 32-bit Windows applications on Windows 64-bit.
The 64-bit versions of Windowssupport applications in WOW64 to support Exchange. The only requirement is that kernel mode components of those applications have to work, so those have to be x64. The main application can be 32 bit running in WOW64. In our opinion, any third-party tools and utilities that run on an Exchange 2007 server should be 64-bit versions.
The Move to 64-Bit Architecture
The move to a 64-bit architecture has been a controversial decision on the part of Microsoft, but in our opinion this certainly makes a lot of sense. Additional accessible memory is the number one reason for moving to the 64-bit architecture. Exchange 2003 Server quickly becomes short on RAM available for caching and other Exchange operations. Microsoft could not add too many additional server-side features to Exchange 2007 without getting around this constraint.
Although the 32-bit architecture certainly leaves a lot of room to grow when fewer mailboxes per server are supported, servers with more mailboxes begin to hit limitations. Microsoft was faced with a decision to support both 32-bit and 64-bit versions of Exchange or to require everyone to move to the 64-bit version. Supporting two different processors' architectures for the same product is both more difficult and more costly than supporting a single version. This is certainly the case with Microsoft, but it is true to a certain degree for the customer as well. As third-party products are released, as fixes are released, and as customizations or tweaks are documented, there will be more possible choices for processors, editions, and operating systems and the customer's support responsibilities will become more difficult.
Room to Grow
For servers supporting larger numbers of mailboxes, the Exchange team had clearly exceeded the limits of the 32-bit architecture with Exchange 2003. Adding additional server-side processes such as messaging records management, improved calendaring and scheduling, transport rules, Unified Messaging services, integration with Windows Rights Management Services, and other new features would not have been possible without additional room to grow.
Improved Caching and Reduced I/O Profiles
Even on a server with only a few hundred mailboxes, Exchange Server 2000/2003 quickly reaches the maximum amount of RAM available for caching (1.2GB maximum). As more and more users vie for the same physical memory for caching, Exchange Server quickly becomes constrained by the amount of I/O (input output) operations that the Exchange server's disk subsystem can support.
Hundreds of pages of material have been written on the concept of optimizing Exchange Server for maximizing performance by improving I/O performance with Exchange, and we certainly can't do the concept justice in just a few paragraphs, but understanding the basic input/output per second (IOPS) requirements of users is helpful. Microsoft and hardware vendors have done much research on I/O requirements based on the mailbox size and the average load that each user places on the server. Table 2.5 shows the estimated IOPS given a user type and an estimated mailbox size for Exchange 2003. IOPS requirements climb as the number of messages sent and received increases and as the mailbox size increases.
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| User Type | Database Volume IOPS | Messages Sent/Received per Day | Mailbox Size |
|---|---|---|---|
| Light | .5 | 20 sent/50 received | 50MB |
| Average | .75 | 30 sent/75 received | 100MB |
| Heavy | 1.0 | 40 sent/100 received | 200MB |
| Large | 1.5 | 60 sent/150 received | 500MB |
|
For an Exchange 2003 server that is supporting 3,000 heavy mailbox users, the disk subsystem would have to support at least 3,000 IOPS. In order to meet this requirement, the disk subsystem may have too many additional disks; thus, the disk subsystem may have far more disk space than is actually necessary in order to support the IOPS profile. Failure to plan for sufficient IOPS capacity on the disk subsystem will significantly hurt performance.
The 64-bit architectural improvements to Exchange 2007 allow the operating system and Exchange Server 2007 to access more physical memory. With additional physical memory available for caching, disk I/O is significantly reduced. Microsoft estimates that I/O requirements are reduced by approximately 70 percent provided the Exchange 2007 server has the recommended amount of RAM. Table 2.6 shows the estimated IOPS requirements for Exchange 2007 Mailbox servers. Please keep in mind that these are estimates and may change over time. These numbers are also calculated when the Mailbox server is configured with more than the recommended amount of RAM.
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| User Type | Database Volume IOPS | Messages Sent/Received per day | Mailbox Size |
|---|---|---|---|
| Light | .14 | 20 sent/50 received | 50MB |
| Average | .20 | 30 sent/75 received | 100MB |
| Heavy | .27 | 40 sent/100 received | 200MB |
| Large | .41 | 60 sent/150 received | 500MB |
|
With this significant improvement in caching Exchange data, the Extensible Storage Engine (ESE) database engine needs to read and write from the disk less frequently and thus reduces the IOPS requirements. When the IOPS requirements are reduced, fewer disks are required to support the I/O load.
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