System information

capacity of the smallest member disk in a Hardware RAID or the capacity of smallest
member partition in a Software RAID multiplied by the number of disks or partitions in the
array.
Level 1
RAID level 1, or "mirroring," has been used longer than any other form of RAID. Level 1
provides redundancy by writing identical data to each member disk of the array, leaving a
"mirrored" copy on each disk. Mirroring remains popular due to its simplicity and high level
of data availability. Level 1 operates with two or more disks, and provides very good data
reliability and improves performance for read-intensive applications but at a relatively high
cost. ⁠
The storage capacity of the level 1 array is equal to the capacity of the smallest mirrored
hard disk in a Hardware RAID or the smallest mirrored partition in a Software RAID. Level 1
redundancy is the highest possible among all RAID types, with the array being able to
operate with only a single disk present.
Level 4
Level 4 uses parity ⁠ concentrated on a single disk drive to protect data. Because the
dedicated parity disk represents an inherent bottleneck on all write transactions to the RAID
array, level 4 is seldom used without accompanying technologies such as write-back
caching, or in specific circumstances where the system administrator is intentionally
designing the software RAID device with this bottleneck in mind (such as an array that will
have little to no write transactions once the array is populated with data). RAID level 4 is so
rarely used that it is not available as an option in Anaconda. However, it could be created
manually by the user if truly needed.
The storage capacity of Hardware RAID level 4 is equal to the capacity of the smallest
member partition multiplied by the number of partitions minus one. Performance of a RAID
level 4 array will always be asymmetrical, meaning reads will outperform writes. This is
because writes consume extra CPU and main memory bandwidth when generating parity,
and then also consume extra bus bandwidth when writing the actual data to disks because
you are writing not only the data, but also the parity. Reads need only read the data and
not the parity unless the array is in a degraded state. As a result, reads generate less traffic
to the drives and across the busses of the computer for the same amount of data transfer
under normal operating conditions.
Level 5
This is the most common type of RAID. By distributing parity across all of an array's
member disk drives, RAID level 5 eliminates the write bottleneck inherent in level 4. The only
performance bottleneck is the parity calculation process itself. With modern CPUs and
Software RAID , that is usually not a bottleneck at all since modern CPUs can generate
parity very fast. However, if you have a sufficiently large number of member devices in a
software RAID5 array such that the combined aggregate data transfer speed across all
devices is high enough, then this bottleneck can start to come into play.
As with level 4, level 5 has asymmetrical performance, with reads substantially
outperforming writes. The storage capacity of RAID level 5 is calculated the same way as
with level 4.
Level 6
This is a common level of RAID when data redundancy and preservation, and not
performance, are the paramount concerns, but where the space inefficiency of level 1 is not
acceptable. Level 6 uses a complex parity scheme to be able to recover from the loss of any
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