Acer Altos EasyStore - Responding to RAID Degradation; Responding to RAID Failure

Altos eas
y
Store Manua
l
Appendix
B Disk Configurations
146
You can use RAID 5 only if your storage system has a t least three disks. If the
disks
are not the same size, the smallest of the disks determines how much disk
space
is available for data. For example, if one disk is 300 GB, one is 400 GB,
and
one is 500 GB, only 300 GB from each disk can be used. Two thirds of each
disk
(200 GB) is used for storage space , and the remaining third is used for
parity informa t ion. As a result , for all three disks, only 600 GB o f disk space
would be available for da t a .
l RAID 5 + spare —In this configuration, three of the disks use RAID 5, and the
fourth
is empty . If any of the three disks fails, it is immediately rebuilt using the
fourth
spare disk. As a result, you can remove the f ailed disk and still have the
ongoing
fast performance and data protection offered by RAID 5. When the
failed disk is repaired or replaced and re-ins t alled into the storage system , it
automatically becomes the spare for the other functioning three.
You can use RAID 5 + spare only if your storage system has four disks. If the disks
are not the same size, the smallest of the disks determines how much disk space is
available for data, similar to RAID 5.
l RAID 10 —RAID 10 is similar to RAID 1, but rather than having one disk mirror
to one other disk, two disks mirror to the two other disks.
You can use RAID 10 only if your storage system has four disks. The disks in the
first two slots constitute the first pair , and t he disks in the second two slots
constitute
the second pair . In each pair , t he smaller of t he two disks is used for
da t a , and the larger of the two disks is used as the mirror .
If one disk in the pair fails, the o t her disk con t inues to make it s da t a available.