HP StorageWorks 2000 Series Reference Manual page 81

To configure dynamic spares:
1. Select Manage > General Config > System Configuration.
2. Set Dynamic Spare Configuration to Enabled.
3. Click Change System Configuration.
When Dynamic Spare Configuration is enabled, the Dynamic Spare Rescan Rate
option is displayed. Use the default rescan rate.
4. Click Change System Configuration.
This section describes how to designate available drives as spares for use by one
virtual disk only. It also describes how to return spares to the pool of available
drives.
You can add a maximum of four available drives to a redundant virtual disk (RAID
1, 3, 5, 6, 10, and 50) for use as spares. If a drive in the virtual disk fails, one of
these vdisk spares is automatically used to reconstruct the virtual disk. A spare must
have sufficient capacity to replace the smallest drive in the virtual disk. Vdisk
spares are also called dedicated spares.
The controller automatically uses the vdisk spare for reconstruction of the critical
virtual disk to which it belongs. The virtual disk remains in Critical status until the
parity or mirror data is completely written to the spare, at which time the virtual
disk returns to Fault Tolerant status. For RAID 50 virtual disks, if more than one
sub-vdisk becomes critical, reconstruction and use of vdisk spares occur in the order
sub-vdisks are numbered.
Although using a vdisk spare is the most secure way to provide spares for your
virtual disks, it is also expensive to keep a spare assigned to each virtual disk. An
alternative method is to enable dynamic spares or to assign one or more unused
drives as global spares.