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VMs per Datastore up-to-date considerations

  • 1.  VMs per Datastore up-to-date considerations

    Posted Mar 31, 2023 06:47 PM

    Hello All,

    Here I am at the crossroads of migrating our old SANs to new ones.
    I now have the required license to enable Datastore Clusters / Storage DRS, and our new SANs are some powerful beasts like HP Nimble and Primera.

    Back in time, we used to have Datastores of 1 ~ 4 TB and were trying to keep less than 20 VMs per datastores. Many years later VMs were growing, and we now have some 8 to 16TB Datastores and some with more than 30 VMs per datastore. Bigger VMs are in the range of 10 to 16 TB (no worries - a handful of them over 500+ VMs.). Of course, we do suffer of "slower SAN performance" on our lower tier but nothing alarming (below 15ms during peek time).

    Now, back to our migration. Is there a current consensus on what we "should" achieve on those newer SANs over Fiber Channel?

    1) Should we still try having Datastores with 20 VMs or so regardless of very low IOPs / data usage? In other terms would it still be considered "best practice" to have 80 VMs on a 16TB LUN while it is consuming very low IOPs?

    2) Should we rather mix smaller Datastores with bigger ones in the Datastore cluster and let DRS handle it?
    My initial "guess" was to trust technology, and have 16TB x 10 LUNs in the Datastore cluster for each tier, but in this case, I will end-up with some datastores with more than 50 VMs...

    Any input will be welcome in that dilemma....