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Appendix A: Disk Configurations
Your storage system supports the following types of disk configurations:
• Linear: A linear configuration is similar to using multiple hard disks in a regular computer.
Each disk is an independent entity, and the data on it is self-contained. You can add or
remove the disks without affecting the other disks. All the available disk space is used for
data.
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.
• RAID 0: Instead of writing all the data to one disk in a linear fashion, 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 at least two disks. However, you can use
RAID 0 with three or four disks as well, and the disks can be any size.
• RAID 1: In this configuration, 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 data is still intact on the
other disk. However, using RAID 1 means only half your available disk space is used for
data; the other half 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 of 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 to make its data available.
• RAID 5: Like RAID 0, RAID 5 offers increased performance by distributing the data across
multiple disks. But unlike RAID 0, RAID 5 also offers data protection. If your storage
system has three disks of equal size, two thirds of each disk 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 disks fails, it can be reconstructed when a new disk is
installed in the storage system.
If your storage system has four disks of equal size, three fourths of each disk 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 disks fails, it can be reconstructed when a new disk is
installed.