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8 Dell PS Series Storage: Choosing a Member RAID Policy | TR1020 | v 4.7
 Excellent = 1.19 or greater
 Fair = 0.x to 1.18
 Poor = 0 and below
SANHQ representation of array reliability
SAN Headquarters RAID Policy Reliability Score
The RAID policy reliability score in SAN Headquarters is calculated at the member level from the drive speed,
size, disk mean time between failure (MTBF) hours, controller type, RAID policy, RAID geometry (number of
disks in each RAID set), workload, and rebuild times. These factors result in a calculated score ranging from
approximately –5.00 to +5.00. A score of 1.19 is the threshold that Dell recommends as a reliable RAID policy
for the group. For example, the threshold score validates the maximum disk configuration in a RAID 50 policy
for a single member. A RAID policy with a score higher than 1.19 increases that effectiveness.
Note: Remember to consider other aspects of the storage system, like capacity and performance, when
choosing a reliable RAID policy.
For more information on using SANHQ and FAQs on RAID reliability see the “RAID Policy Evaluation and
Reliability” section in the latest version of the SAN Headquarters Installation and User’s Guide at
http://eqlsupport.dell.com then “Downloads->SAN Headquarters”.