User manual

WebPAM User Manual
82
Data Drives Parity Drive
1 parity
2 parity
3 parity
4 parity
1c
2c
3c
4c
1b
2b
3b
4b
1a
2a
3a
4a
Data Stripes
Figure 108. RAID 3 Stripes Data and adds a dedicated Parity Drive
The capacity of a RAID 3 array is the smallest drive size multiplied by the number
of drives less one. Hence, a RAID 3 array with (4) 100 GB hard drives will have a
capacity of 300GB. An array with (2) 120GB hard drives and (1) 100GB hard
drive will have a capacity of 200GB.
RAID 5 - Block and Parity Striping
RAID 5 is similar to RAID 3 as described above except that the parity
data is distributed across the physical drives along with the data blocks.
In each case, the parity data is stored on a different disk than its
corresponding data block.
RAID 5 makes efficient use of hard drives and is the most versatile
RAID Level. It works well for file, database, application and web servers.
4b
4c
4d
a parity
3a
3c
3d
b parity
2a
2b
2d
c parity
1a
1b
1c
d parity
Disk Drives
Distributed Parity
Data
Blocks
Figure 109. RAID 5 Stripes all Drives with Data and Parity
Information