Technical information

31 EqualLogic Configuration Guide | Version 15.2 | August 2014
7.5 Array RAID configurations and associated RAID sets
The tables show a logical drive layout when an array is initialized for the first time. The actual physical
layout of drives can change and evolve due to maintenance and administrative actions. Spare drives can
move as they are utilized to replace failed drives and newly added drives become the spares. It is not
possible to determine which physical drives are associated with each RAID set. This information is dynamic
and maintained by the EqualLogic firmware.
Table 10 shows the RAID set relationship for each RAID type in a 24-drive configuration.
Table 10 EqualLogic PS Series array RAID types and RAID set relationships
RAID policy
Spare disks
RAID set relationship
Best practice
RAID 6
1 Spare Disk
(10+2) (9+2)
Yes
RAID 10
2 Spare Disks
(6+6) (5+5)
Yes
RAID 50
2 Spare Disks
(5+1, 5+1) (4+1, 4+1)
For selected configurations
RAID 5
1 Spare Disk
(12+1) (9+1)
Not for business critical data
Table 11 shows the RAID set relationship for each RAID type in a 48-drive configuration.
Table 11 EqualLogic PS Series array RAID types and RAID set relationships
Raid policy
Spare disks
Raid set relationship
Best practice
RAID 6
1 Spare Disk
(12+2, 12+2, 12+2) (3+2)
Yes
RAID 10
2 Spare Disks
(7+7, 7+7, 7+7) (2+2)
Yes
RAID 50
2 Spare Disks
(6+1, 6+1, 6+1, 6+1, 6+1, 6+1) (3+1)
For selected configurations
RAID 5
2 Spare Disk
(12+1, 12+1, 12+1) (6+1)
Not for business critical data
Table 12 shows the RAID set relationship for each RAID type in a 16-drive configuration.
Table 12 EqualLogic PS Series array RAID types and RAID set relationships
Raid policy
Spare disks
Raid set relationship
Best practice
RAID 6
1 Spare Disk
(13+2)
Yes
RAID 10
2 Spare Disks
(7+7)
Yes
RAID 50
2 Spare Disks
(6+1, 6+1 )
For selected configurations
RAID 5
1 Spare Disk
(14+1)
Not for business critical data