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Appendix B
146
You can use RAID 5 only if your storage system has at 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 information. As a result, for all three disks, only 600 GB of disk space
would be available for data.
RAID 5 + spare—In this configuration, three of the disks use RAID 5, and the
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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 failed 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-installed 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.
RAID 10—RAID 10 is similar to RAID 1, but rather than having one disk mirror
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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 the disks in the second two slots
constitute the second pair. In each pair, the smaller of the two disks is used for
data, and the larger of the two disks is used as the mirror.
If one disk in the pair fails, the other disk continues to make its data available.
Disk Configurations
Altos easyStore Manual
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