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7 Dell PS Series Storage: Choosing a Member RAID Policy | TR1020 | v 4.7
RAID reliability scores for different PS Series disk types
NOTE: The y-axis is the relative average reliability score for several PS Series disks. RAID 5 is deliberately
left off this graph to reflect current PS Series best practices.
Key observation: RAID 6 demonstrates a much greater reliability than other RAID types. The extreme
reliability of RAID 6 is due to its ability to protect against a double disk failure, where a read error occurs or a
second disk fails during rebuild of failed disk. As disk counts and capacities have increased, RAID 6 has
become a more important practice to ensure overall data protection in storage arrays.
The reliability scores in the graphic above represent relative reliability for a given RAID choice based on type
of disks, the number of disks in the RAID set, rebuild times for the RAID set, and the possibility of a second
disk (or 3
rd
if RAID 6) failing during a RAID rebuild operation.
SAN Headquarters v2.6 and later includes this intelligence to enable a higher level of awareness for
customers that are concerned about RAID reliability and how they have their PS Series groups configured.
SANHQ will measure the reliability score of an array from -5 to 5 and give it a rank of Excellent, Fair or Poor
based on the score.
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
12.0
400 GB
SSD
800 GB
SSD
600 GB
15K
1.2 TB
10K
1 TB
7.2K
3 TB
7.2K
4 TB
7.2K
6 TB
7.2K
RAID 6 RAID 10 RAID 50