Supported Load With Exchange; Sample Iscsi Nas Microsoft Exchange Server 2003 Configuration - HP StorageWorks 4000/6000/8000 - Enterprise Virtual Arrays Reference Manual

RAID level
For database volumes, the choice of RAID protection on the disk arrays is a trade-off between maximum
storage and performance. For the same number of disk spindles, RAID 5 provides data protection
and maximum storage, and RAID 1+0 provides the best performance but with less storage.
Six spindles in a RAID 1+0 array provide greater performance than six spindles in a RAID 5 array
for a given number of Exchange mailboxes. RAID 1+0 is preferred for the database volume. Using
six 36 GB drives in a RAID 1+0 array provides ample storage and performance for a thousand 100
MB mailboxes.
Designing storage arrays with the large disk drives (146 GB or larger) requires caution. Although a
few large disks can provide the required amount of database storage, the reduced spindle count will
decrease I/O performance.
Write-back caching
Write-back caching increases performance for transaction logs on the server array and for databases
on the storage array. On array controllers with battery-backed write cache (such as the Smart Array
5i Plus and later) the write-cache percentage should be set to 100%.
Recommendations
HP recommends that you:
Place the Exchange log files and database files on separate RAID 1+0 RAIDsets.
Place the Exchange log files on Exchange server disks.
Use hardware RAID controllers with write-back caching.

Supported load with Exchange

The performance required by the average email user determines the storage design. The average
load is multiplied by the number of users to find the storage requirement. Conversely, the capabilities
of an existing system can determine the maximum number of users.
To calculate the average I/O per user in an Exchange environment, the PERFMON object's
disk-transfers-per-second value is divided by the number of active connections. The storage capacity
calculated from the average I/O needs an additional safety factor to maintain performance during
peak periods.
In practice, the maximum number of users is less than the calculated value when:
Users increase the size of their mailboxes.
Services such as antivirus scanners or content indexers are added to the Exchange server.
A medium-sized user profile provides a 60 MB mailbox, and a large profile provides a 100 MB
mailbox. Larger mailboxes affect both storage sizing and performance, and are disproportionately
more difficult for Exchange to manage.

Sample iSCSI NAS Microsoft Exchange Server 2003 configuration

This section summarizes results from an HP-tested iSCSI NAS configuration. Details of this test are
available at http://storage.corp.hp.com/Document_Storage/whitepapers/new_library/
5982-9399EN_Exchange_2003_HP_iSCSI_and_WSS_NAS_WP.pdf.
SAN Design Reference Guide 393