vBlock Tip: vSphere 5, SIOC, EMC FAST VP and Storage DRS


If you’ve got a vBlock its most likely you’ve got an EMC array with EMC FAST VP and hopefully by now you’ve upgraded to vBlock Matrix 2.5.0 and you’re using vSphere 5.

If not, what are you waiting for? Oh yeah, there are still a few outstanding issues.  (My advice wait for the Storage vMotion issues to be resolved, its a real pain.)

I wanted to post some best practices and recommended settings for leveraging VMware’s Storage IO Control with EMC Fast VP and Storage DRS.

First a quick recap:

  • FAST VP is EMC’s sub LUN auto-tiering mechanism.
  • SIOC is VMware’s attempt to leverage the idea of DRS (distributed resource prioritisation) into the storage layer. SIOC  provides I/O performance monitoring and isolation of virtual machines in vSphere 5.
  • Storage DRS is a new feature in vSphere 5 which allows datastores to be pooled together as a single resource.

The bottom line: EMC FAST VP and SIOC are not only compatible but can work together harmoniously because they serve different purposes.

EMC FAST monitors data usage over an hourly period and only moves data once every 24 hours. Unlike SIOC, EMC FAST redistributes data based on the 1GB slice usage and lowers the response time of the busiest slices.

Compared to EMC FAST, SIOC uses a relatively short sampling window and is designed to quickly deal with short term IO contention crises. It can act quickly to throttle IO to limit guest latency during times of IO contention.

SIOC and EMC FAST perform complementary roles to monitor and improve storage performance, therefore they should both be leveraged in your environment.

And lastly Storage DRS – should it be used — yes, but  in what capacity?

My recommendation is to leverage Storage DRS in Automatic mode for initial placement to balance VMs evenly across datastores. I would also enable SDRS to monitor free capacity to make VM relocation recommendations if datastores approach capacity. The default setting is 90% which should be adequate.

What should be disabled though is IO Metrics — It is EMC’s recommendation Storage DRS IO metrics be disabled when using FAST VP. This is because they will perform competing roles, potentially identifying similar relocations and cause inefficient use of storage system resources.

So there you have it. The best way to leverage these components in your vBlock.

Sources:

There is a great EMC document here which lists best practice with EMC VNX Storage and vSphere and an old, but relevant article from Virtual Geek on SIOC and auto-tering.

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