Apple Xserve RAID - Manual (Page 70)

Planning RAID Storage for the Xserve RAID System 71
RAID 1 Schemes
You can use RAID 1 several ways, depending on how you divide the drive modules between
the RAID controllers, how you choose to mirror the drives, and where you put the module
you use as a hot spare. The hot spare is a drive that the RAID controller automatically uses to
rebuild data if another drive fails. The hot spare is only available to mirrored pairs on the
same controller. If all the drive modules are on one controller, the drives can be mirrored in
pairs, and the hot spare will be available to all three pairs.
If four modules are on the first controller and three modules are on the second controller,
the drives on each controller can be mirrored in pairs, with one module as a hot spare for
the pair on the second controller.
RAID 1
Mirror Mirror Mirror Hot spare
Disk 3
Appears
as
Disk 1 Disk 2
RAID 1
Mirror Mirror Mirror Hot spare
Disk 3
Appears
as
Disk 1 Disk 2