A. Exchange Server is effectively a service to a back-end database--the Extensible Storage Engine (ESE); thus, disk performance is a major factor in the performance of your Exchange Server implementation. It's therefore vital that you segregate your OS, transaction logs, and database in an optimal configuration, as follows:
- OS (includes the Exchange Server binaries): RAID 1 (mirrored)
- Storage group (SG) transaction logs: RAID 1 (mirrored)--Each SG has its own transaction logs and should have separate physical disks. The disks that comprise the RAID 1 drive should be on separate controllers to avoid bottlenecks during write operations. RAID 1 is used instead RAID 5 because RAID 1 performs better for write operations.
- Databases: RAID 5 (striped with parity)--RAID 5 performs better for multiple-read environments, such as databases. An alternative to using RAID 5 for database storage is to use RAID 0+1, which is a stripe set without parity. The disks that comprise the stripe set are mirrored. However, sites typically don't choose to use RAID 0+1 for databases because of their high cost (i.e., half of the disk space isn't usable).