6 Responses

  1. blocksandbytes
    blocksandbytes at |

    Great article.

    Good to hear SIOC is supported with EMC FAST (just in case) and thanks for clarifying it should be disabled under normal circumstances.

    Like you we use Storage DRS to manage initial placement of VMs onto FAST VP (VNX 7500) storage and currently IO Metrics is disabled.

    1. @vcdxnz001
      @vcdxnz001 at |

      Hi Gareth, SIOC should be enabled. It will help smooth out any unacceptably high latency peaks. But you should have storage metrics disabled in Storage DRS when using FAST. These are two quite different things. SIOC Yes, Storage Metrics on SDRS when using FAST NO.

      1. blocksandbytes
        blocksandbytes at |

        Ok, thanks. Getting confused there. All our non-replicated datastores reside in Storage DRS and our replicated datastores outside Storage DRS as its not compatible with SRM 5.

        Currently we have SIOC enabled on all our non-replicated datastores with Storage DRS IOMetrics disabled, but we have had to disable SIOC on all our replicated datastores (outside Storage DRS) as otherwise we have found that SRM cannot unmount the datastore.

  2. Garret Black
    Garret Black at |

    We just migrated VM's to datastores on a VMAX with FASTVP. I was planning on keeping SIOC off. My reasoning is we have some pretty large SQL VM's that have high IOPS and in turn higher response times. I'm assuming that SIOC is going to throttle them back when it doesn't neccessarily need to. My other reason is the annoying SIOC eternal IO alarm that is pretty noisy in the logs even if you turn the alarm off. We are migrating off a AMS2500 that served datastores only in this vcenter, which by documentation says vcenter should know where the IO is. Unfortunately after talking with HDS it's not quite the case when using disk pools which spread the data across all disks in a 42MB chunk. There has to be some kind of overhead with SIOC as well so if it's not doing much if any good why keep it on?

    After reading this i'm re-thinking turning SIOC on since we just bumped up to 6TB datastores. We will have anywhere between 1 and 20 VM's on each datastore.

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