Acer Altos EasyStore - Page 152

Altos eas
y
Store Manua
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145
Disk Configurations
B
Your storage system supports various types of disk configurations, including RAID
(redundan t array of independent disks), a disk subsystem tha t can increase
performance,
provide da t a protection, or both .
l Linear —A linear configuration is similar to using multiple hard disks in a regular
compu
t er . Each disk is an independent entity , and the da t a on it is self-
contained. You can add or remove the disks withou t affecting the other disks. All
the available disk space is used for da t a .
If your storage system has only one disk , you must use a linear configuration.
However
, you can use a linear configuration for two , three , or four disks as well.
l RAID 0 —Instead of writing all the da t a to one disk in a linear f ashion, some
bytes
are written to one disk, and other bytes are written to another .
Performance is faster because reading and writing activities can occur on
multiple
disks simultaneously . All the available disk space is used for data.
For RAID 0, your storage system must have a t leas t two disks. However , you
can use RAID 0 with t hree or f our disks as well, and the disks can be any size .
l RAID 1 —In t his con f igura t ion, all the data written to one disk is duplicated on the
other
disk. This offers greater data protection since if one disk fails, all your da t a
is still intact on the other disk. However , using RAID 1 means only ha lf your
available
disk space is used for data; the other ha lf is used for a duplicate
(mirror)
of that data .
You can use RAID 1 only if your storage system has only two disks. If the disks
are
not the same size , the smaller o f the two disks is used for data, and the
larger of the two disks is used as the mirror .
If one disk fails, the other disk continues t o make it s data available .
l RAID 5 —Like RAID 0, RAID 5 offers increased performance by distributing t he
da
t a across multiple disks. Bu t unlike RAID 0, RAID 5 also of f ers da t a
pro t ection. If your storage system has three disks of equal size, two thirds o f
each disk are used for data, and the remaining third contains the parity
informa
t ion needed to reconstruct either of the other t wo . In this way , if any of
the three disks f ails, it can be reconstructed when a new disk is installed in the
storage
system.
If your storage system has four disks o f equal size, three fourths of each disk
are
used for da t a , and the remaining fourth contains the parity informa t ion
needed
to reconstruc t either of the other three. If any of t he four disks fails, it
can be reconstructed when a new disk is installed .