A SAN unit stored the data for the Internet Platform and Operations group deployment of Windows SharePoint Services. The unit comprised switches, two controllers, and three Proliant disk shelves, each of which housed fourteen 36.4-GB hard disk drives. The raw capacity of the SAN was 509.6 GB per shelf, or approximately 1.5 terabytes (TB) in total.

Figure 4 and Table 3 show how the SAN drives were allocated. Unused drives – 105, 302, 402, 500, 504, 600, 601, and 604 – are shown as white rectangles.

Figure 4 – SAN disk layout

Table 3 – Key to SAN disks

All drives except those used for backups (database or transaction logs) used RAID 1+0 (striping with mirroring). This maximizes input/output performance while still retaining recoverability for database files in the event of disk failures. Backup and log disks used RAID 5 for maximum performance and recoverability, and the quorum uses RAID 1 (mirroring).