A. Spend money on the I/O subsystem because I/O performance is most often the bottleneck for heavily loaded servers. Your dollars can also buy a good bit of hardware-level redundancy if you choose the right configuration.
Most Exchange Server experts would agree on the following configuration:
- two mirrored disks (at least 4GB each) for the OS and page file. Mirroring gives you redundancy.
- two mirrored disks (at least 4GB each for most servers—less for connector-only servers, more for very active servers) for transaction logs. Mirroring gives you redundancy here too, and it's important to keep the log files on a separate drive from the OS and data for both failure survival and performance.
- a RAID 5 array (N disks, 9GB or larger for most applications) for the Information Store (IS) databases. Hardware RAID provides superior performance and redundancy, but limping along with Windows NT's software RAID is better than nothing.