Optimizing an Exchange Server 2007 Environment : Properly Sizing Exchange Server 2007

The core components of Exchange Server (for example, the Information Stores, connectors, transaction logs, and more) have a direct bearing on gauging resource requirements. The number of users in a messaging environment and the various Exchange functions are equally influential.

Optimizing the Disk Subsystem Configuration

Many factors, such as the type of file system to use, physical disk configuration, database size, and log file placement, need to be considered when you are trying to optimize the disk subsystem configuration. The desire for performance must also be balanced with the requirements for redundancy and revocability.

Choosing the File System

Among the file systems supported by Windows Server 2003 (that is, FAT and NTFS), it is recommended to use only NTFS on all Exchange 2007 servers. NTFS provides the best security, scalability, and performance features. For instance, NTFS supports file- and directory-level security, large file sizes (files of up to 16TB), large disk sizes (disk volumes of up to 16TB), fault tolerance, disk compression, error detection, and encryption.

Choosing the Physical Disk Configuration

Windows Server 2003, like its predecessors, supports RAID (Redundant Array of Inexpensive Disks). The levels of RAID supported by the operating system are as follows:

• RAID 0 (Striping)

• RAID 1 (Mirroring)

• RAID 5 (Striping with parity)

Various other levels of RAID can be supported through the use of hardware-based RAID controllers.

The deployment of the correct RAID level is of utmost importance because each RAID level has a direct effect on the performance of the server. From the viewpoint of pure performance, RAID level 0 by far gives the best performance. However, fault tolerance and the reliability of system access are other factors that contribute to overall performance. The skillful administrator strikes a balance between performance and fault tolerance without sacrificing one for the other. The following sections provide recommended disk configurations for Exchange Server 2007.

Disk Mirroring (RAID 1)

In this type of configuration, data is mirrored from one disk to the other participating disk in the mirror set. Data is simultaneously written to the two required disks, which means read operations are significantly faster than systems with no RAID configuration or with a greater degree of fault tolerance. Write performance is slower, though, because data is being written twice; once to each disk in the mirror set.

Besides adequate performance, RAID 1 also provides a good degree of fault tolerance. For instance, if one drive fails, the RAID controller can automatically detect the failure and run solely on the remaining disk with minimal interruption.

The biggest drawback to RAID 1 is the amount of storage capacity that is lost. RAID 1 uses 50% of the total drive capacity for the two drives.

Disk Striping with Parity (RAID 5)

In a RAID-5 configuration, data and parity information is striped across all participating disks in the array. RAID 5 requires a minimum of three disks. Even if one of the drives fails within the array, the Exchange Server 2007 server can still remain operational.

After the drive fails, Windows Server 2003 continues to operate because of the data contained on the other drives. The parity information gives details of the data that is missing because of the failure. Either Windows Server 2003 or the hardware RAID controller also begins the rebuilding process from the parity information to a spare or new drive.

RAID 5 is most commonly used for the data drive because it is a great compromise among performance, storage capacity, and redundancy. The overall space used to store the striped parity information is equal to the capacity of one drive. For example, a RAID-5 volume with three 200-GB disks can store up to 400GB of data .

Hardware Versus Software RAID

Hardware RAID (configured at the disk controller level) is recommended over software RAID (configurable from within the Windows Server 2003) because of faster performance, greater support of different RAID levels, support for caching, and capability of recovering from hardware failures more easily.

Database Sizing and Optimization

Exchange Server 2007 is available in two versions: Standard and Enterprise. The Standard Edition supports one storage group with one private and one public Information Store. The maximum Information Store (database) size is 75GB with Exchange Server 2007, Standard Edition. The Enterprise Edition provides support for up to 50 storage groups with a combined total of 50 usable databases per server with practically unlimited database size. Technically, the databases are limited to 16,000GB but it’s unlikely that you’ll grow them that large. Unlike with previous versions of Exchange, it is currently recommended that for performance and recoverability purposes, you should only place one database into each storage group.

The flexibility with the Enterprise Edition is beneficial not just in terms of growth but also in terms of performance and manageability. More specifically, the advantages for segmenting can include the following:

• Administrators are enabled to segment the user population on a single Exchange server.

• Multiple mailboxes can more evenly distribute the size of the messaging data and help prevent one database from becoming too large and possibly unwieldy for a given system.

• Multiple databases present greater opportunities for faster enumeration of database indexing.

• Multiple databases can be segmented onto different RAID volumes and RAID controller channels.

• Transaction logs can be segmented from other log files using separate RAID volumes.

• Failures such as database corruption affect a smaller percentage of the user population.

• Offline maintenance routines require less scheduled downtime, and fewer users are affected.

Determining the number of storage groups and databases for Exchange Server 2007 Mailbox servers should also be based on workload characterization. Users can be grouped based on the how they interact with the messaging system (for example, in terms of frequency, storage requirements, and more). Users placing higher demands on Exchange Server 2007 can be placed into a separate storage group and separate databases so that the greater number of read/write operations do not occur in the same database and are more evenly distributed. This is beneficial to performance only if the storage groups and databases are located on physically different disks.

If a deployment calls for a large number of storage groups and databases, it is necessary to mount disks as mount points rather than as drive letters or you would quickly run out of drive letters before utilizing all 50 of your potential storage groups.

Optimizing Exchange Logs

Similar to the previous versions of Exchange, transaction log files should be stored on separate RAID volumes. This enables significant improvements in disk input/output (I/O) operations. Transaction logs are created on a per–storage group level rather than per database. Therefore, when you have multiple storage groups, multiple log files are created that enable simultaneous read and write operations. If the transaction logs are then placed on separate RAID volumes, there can be significant improvements to performance.

Sizing Memory Requirements

The recommended starting point for the amount of memory for an Exchange Server 2007 server is 2GB of RAM per server + 5MB of RAM per user. The specific memory requirements naturally vary based on server roles, server responsibilities, and the number of users to support. In addition, some organizations define certain guidelines that must be followed for base memory configurations. A more accurate representation of how much memory is required can be achieved by baselining memory performance information gathered from the Performance snap-in or third-party tools during a prototype or lab testing phase.

Another important factor to take into consideration is when the organization adds functionality to Exchange Server 2007 or consolidates users onto fewer servers. This obviously increases resource requirements, especially in terms of adding more physical memory. In these scenarios, it is recommended to use the base amount of memory (for example, 8GB) and then add the appropriate amount of memory based on vendor specifications. It is also important to consult with the vendor to determine what the memory requirements might be on a per user basis. This way, the organization can plan ahead and configure the proper amount of memory prior to needing to scale to support a larger number of users in the future.

Sizing Based on Server Roles

Server roles can have a considerable bearing on both the performance and capacity of Exchange Server 2007. Based on the various roles of the Exchange servers, the strategic placement of Exchange services and functionality can greatly improve performance of the overall messaging system while reducing the need for using additional resources. By the same token, a misplaced Exchange service or functional component can noticeably add to network traffic and degrade the overall performance of the messaging system.

Servers are divided into five roles: Client Access servers, Mailbox servers, Hub Transport servers, Edge Transport servers, and Unified Messaging servers.

Mailbox Server Sizing

Various factors affect the performance of a Mailbox server, including the following:

• The number and type of protocols supported

• The number of users supported

• The authentication methods supported

• Encryption requirements

Table 1 shows the recommended resource requirements of Mailbox servers. It is important to note that these guidelines are minimum recommendations, and actual requirements might vary depending upon the organization.

Client Access Server Sizing

Various factors affect the performance of a Client Access server, including the following:

• The number and type of protocols supported

• The number of type of applications supported

• The number of users supported

• The authentication methods supported

• Encryption requirements

Table 2 shows the recommended resource requirements of Client Access servers. It is important to note that these guidelines are minimum recommendations, and actual requirements might vary depending upon the organization.

Hub Transport Server Sizing

Various factors affect the performance of a Hub Transport server, including the following:

• The number and type of protocols supported

• The number of users supported

• The authentication methods supported

• Encryption requirements

Table 3 shows the recommended resource requirements of a Hub Transport server. It is important to note that these guidelines are minimum recommendations, and actual requirements might vary depending upon the organization.

Edge Transport Server Sizing

Various factors affect the performance of an Edge Transport server, including the following:

• The number of messages sent and received

• The types of rules implemented

• The types of filtering performed

• Encryption requirements

Table 4 shows the recommended resource requirements of an Edge Transport server. It is important to note that these guidelines are minimum recommendations, and actual requirements might vary depending upon the organization.

Unified Messenger Server Sizing

Various factors affect the performance of a Unified Messaging server, including the following:

• The number and type of codecs supported

• The number of users supported

• The type of phone system integrated with

Table 5 shows the recommended resource requirements of a Unified Messaging server. It is important to note that these guidelines are minimum recommendations, and actual requirements might vary depending upon the organization.

Combined Role Server Sizing

Various factors affect the performance of an Exchange 2007 server with combined roles, including the following:

• The number and type of protocols supported

• The number of users supported

• The authentication methods supported

• Encryption requirements

Table 6 shows the recommended resource requirements of a combined role Exchange 2007 server. It is important to note that these guidelines are minimum recommendations, and actual requirements might vary depending upon the organization.