EVGA Z790 CLASSIFIED User Manual page 60

EVGA Z790 CLASSIFIED (121-RL-E798)
RAID5
: RAID5 is a stripe with fault tolerance, which attempts to bridge the gap
between speed and redundancy. It is the most all-around type of array. This array-type
will reserve, essentially, a capacity size equivalent to one drive for fault-tolerance. This
means that if you use four 1TB drives to create your RAID5, you will only have the
capacity of three 1TB drives. RAID5 requires a minimum of three drives, and the
maximum is set by the RAID controller; this level works well when using between four
to six drives, but sees diminishing returns beyond six.
A RAID5 array is still usable even while a drive is missing or failed drive, resulting in a
degraded state. Performance will suffer until the missing drive is replaced and the
software rebuild process is completed. The rebuild process can take several hours,
causing reduced performance during this time.
The Good-

Most capacity-efficient array-type that also has fault tolerance.

Read/write speed is very good; faster than RAID1 but slower than RAID0.
However, speed may vary depending on the number of drives in the array.
The Bad-

Rebuilding an array can take a long time on a motherboard controller, especially
when using a very large capacity array with multiple drives.

If more than one drive fails before repairing the array, the array will fail and data
will be lost.

RAID5 is a good all-around RAID, but it does not excel at performance or
redundancy. Consider a RAID10 for speed and redundancy, instead.
RAID5 protects data by rotating parity across physical drives. Each physical drive
receives small portions of data from other drives and maintains this data in a parity
block of data. When a failed drive is replaced, its data is restored from the parity block
on each of the remaining drives in the array. The repair process copies a very large
volume of small data segments back to the replacement drive while also maintaining the
array's index of data.
A final note regarding capacity – Using drives of different sizes will affect the maximum
capacity of a RAID5. When creating the array, the controller will look at the drive with
the smallest capacity and use this as the size for each drive in the array. For example,
let's say you have three drives – two 1TB drives, one 500GB drive. The array size will be
reduced to 500GB per drive, resulting in a 1TB RAID5 (3x 500GB – 500GB).
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