Acer Altos easyStore M2 User Manual page 255

• RAID 5 — Like RAID 0, RAID 5 offers increased performance by
distributing the data across multiple HDDs. But unlike RAID 0,
RAID 5 also offers data protection. If your storage system has three
HDDs of equal size, two thirds of each HDD are used for data, and
the remaining third contains the parity information needed to
reconstruct either of the other two. In this way, if any of the three
HDDs fails, it can be reconstructed when a new HDD is installed in
the storage system.
If your storage system has four HDDs of equal size, three fourths of
each HDD are used for data, and the remaining fourth contains
the parity information needed to reconstruct either of the other
three. If any of the four HDDs fails, it can be reconstructed when a
new disk is installed.
• RAID 5 + spare — In this configuration, three of the HDDs use RAID
5, and the fourth is empty. If any of the three HDDs fails, it is
immediately rebuilt using the fourth spare HDD. As a result, you
can remove the failed HDD and still have the ongoing fast
performance and data protection offered by RAID 5. When the
failed HDD 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
HDDs. If the HDDs are not the same size, the smallest of the HDDs
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
HDD mirror to one other HDD, two HDDs mirror to the two other
HDDs.
You can use RAID 10 only if your storage system has four HDDs.
The HDDs in the first two slots constitute the first pair, and the
HDDs in the second two slots constitute the second pair. In each
pair, the smaller of the two HDDs is used for data, and the larger
of the two HDDs is used as the mirror.
If one HDD in the pair fails, the other HDD continues to make its
data available.
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