Chapter 6.2.1. Host I/O
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86 SAN Volume Controller: Best Practices and Performance Guidelines 6.1 Back- end queue depth The SAN Volume Controller ( SVC) submits I/ O to the back- end ( MDisk) storage in the same fashion as any direct- attached host. For direct- attached storage, the queue depth is tunable at the host and is often optimized based on specific storage type as well as various other parameters, such as the number of initiators. For the SVC, the queue depth is also tuned; however, the optimal value used is calculated internally. This is the formula SVC uses for calculating queue depth. There are two parts to the algorithm: a per MDisk limit and a per controller port limit. Q = (( P x C) / N) / M If Q > 60, then Q= 60 ( maximum ...
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