HP XP48 Manuel du propriétaire télécharger pdf (Page 105)

RAID Technology

105

Figure 19. Dynamic Sparing and Correction

Dynamic sparing is a method of removing a drive from service if its

read/write errors exceed a certain threshold value. On normal read and

write operations, the array keeps track of the number of errors that occur. If

the error threshold is reached, the system considers that the drive is likely to

cause an unrecoverable error and automatically copies the data from that

drive to a spare disk. The dynamic sparing method used in the XP512 is the

same for both RAID0/1 and RAID5.

Correction copy is invoked when the system encounters an unrecoverable

error occurring on a drive. In RAID5, correction copy will regenerate the

original data for that drive using the data from the other two drives and the

parity data, and then the controller copies the regenerated data onto the

spare disk. In RAID0/1, correction copy just has to copy the data from the

mirrored disk onto the spare disk. After a failed disk has been replaced, the

data is moved back to its original location, and the spare disk is then

available as an active spare.

DKC

Disk 1 Disk 2 Disk 3 Disk 4

Ready to accept

I/O requests

Ready to accept

I/O requests

Ready to accept

I/O requests

DKC (RAID5)

Disk 1 Disk 2 Disk 3 Disk 4

Spare

disk

Spare

disk

Spare

disk

RAID 5

DKC (RAID 0/1)

Disk 1 Disk 2 Disk 3 Disk 4

RAID 0/1

1 2 ... 100 101 102 103 104 105 106 107 108 109 110 ... 123 124

Pas de commentaire

HP XP48 Manuel du propriétaire Page 105