NAS System
8
User’s Manual
Under
RAID 5
parity information is distributed across all the drives. Since there is no
dedicated parity drive, all drives contain data and read operations can be overlapped on
every drive in the array. Write operations will typically access one data drive and one
parity drive. However, because different records store their parity on different drives,
write operations can usually be overlapped.
Dual-level RAID
achieves a balance between the increased data availability inherent in
RAID 1 and RAID 5 and the increased read performance inherent in disk striping (RAID
0). These arrays are sometimes referred to as RAID 0+1 or RAID 10 and RAID 0+5 or
RAID 50.
RAID 6
is similar to RAID 5 in that data protection is achieved by writing parity
information to the physical drives in the array. With RAID 6, however,
two
sets of parity
data are used. These two sets are different, and each set occupies a capacity equivalent
to that of one of the constituent drives. The main advantage of RAID 6 is High data
availability – any two drives can fail without loss of critical data.
