Configuring Dynamic Spare Disks - HP StorageWorks XP48 - Disk Array Owner's Manual

Configuring Dynamic Spare Disks

RAID Technology
You can configure the disk array with a minimum of 1 and a maximum of
16 spare disk drives. For both RAID0/1 and RAID5 array groups, any
dynamic spare drive can back up any other disk drive of the same capacity,
anywhere in the disk array, even if the failed disk and the spare disk are on
different array control processor (ACP) pairs. The RAID system uses
diagnostics and disk-scrubbing algorithms to detect and correct drive
errors. The system can encounter errors with the physical drive either from
a host I/O request or from background data integrity checking.
HOST
D2
D2
D1 D2 D3
D5 D6 P
(4-6)
D9 P
D7
(7-9)
P D10
D11
(10-12)
Disk 1 Disk 2 Disk 3
Figure 17. Normal Data Read Operation
If a drive error occurs during an I/O operation from a host, the system can
recover the target data using parity data and data stored on the other
nonfailing drives. The data can be recovered even when the array
subsystem cannot read the data because of errors occurring on the physical
drives. This feature ensures nondisruptive processing of applications in
case of drive errors. Figure 17 (page 103) shows a normal data read
operation. The figure below shows how data is reconstructed after a drive
error is encountered.
HOST
DKC
(RAID 5)
P D1
(1-3)
D4 M2
D8
D5
D12
M6
Disk 4 Disk 1
D2
DKC
D2
RAID 0/1
M1
D3 M3
D2
M4
D4
M5
D7 M7
D8
D6 M8
Disk 2 Disk 3 Disk 4
103