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  1. Hi,
    I have one question. WE have a VNX7600 storage. Recently we have upgraded its FAST cache from 512GB to 1100GB (Doubled it.) But post upgrade of FAST cache, the utilization of controllers increased by 20-25%. Before the upgrade the utilization on both the controllers were around 50-55% and post upgrade it is 70-75%. Ideally it should decreased. EMC has said it is the normal behaviour post upgrade because whenever FAST cache is upgrade utilization will increase and not decrease. I am not able to understand this. Kindly help in understanding this.

    1. Hi Rajeev,

      It’s hard to say for certain without analyzing your array. I can tell you that The FAST Cache driver has to track every I/O in order to calculate whether a block needs to be promoted to FAST Cache, which adds to the SP CPU utilization. When upgrading FASTCache the cache needs to be deleted and then it slowly recreates after the upgrade as it identifies hot data, which would lead to additional CPU workload at least in the short term. Your best bet for reducing SP utilization would be to Disable FAST Cache for LUNs unlikely to need it, especially LUNs that have sequential I/O, like oracle database logs. I’ll do a complete write-up of FASTCache best practices soon and review the other important things you should take a look at. Thanks for the comment!

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