VMware

esxtop and disk latency

I’m looking into storage latency with esxtop, well vmware top actually for a chartview. I don’t want to look at vm latency as there’s too many vm’s for this vdi setup, so I’m thinking either the lun or the hba would be better for davg, thoughts? vm latency should roll up into those other 2 correct?



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2 Comments

  1. What are your goals, or is there a specific problem you are trying to solve? Knowing what you are trying to accomplish will get you better answers.

    That said, both are useful in their own way in determining the scope of any latency issues. Device latency (***u*** in esxtop) will show you latency aggregated at the LUN level so you can determine if any latency issues are confined to a single disk target. You can get a breakout by adapter by looking at the adapter charts (***d*** in esxtop) – ideally latency should be equal between adapters if they are set up the same and multipath is appropriately configured. Compare DAVG on these to latency reported by your storage to determine if there’s an issue in the fabric somewhere.

    VM-level latency could be unrelated to either – it could be that you are exhausting the queue depth on the guest’s adapter, but that would be something to look at after you eliminate the hardware variable.

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