Oracle ZFS Storage ZS11-2 Storage Drives
Only two of the storage drive slots are used for system boot purposes, which include redundant mirrored drives. These are used and designated consecutively from bottom (System Disk 0) to second from bottom (System Disk 1). The other storage drive slots contain filler panels as indicated in the following figure.

1 System Disk 0 |
2 System Disk 1 |