1 Copper

sharing a LUN across multi vmware ESX clusters?

we have a situation that vmware admins want to have some LUNs shared across two ESX clusters.

    say clusterA = { hostA1, hostA2 .. }, clusterB = { hostB1, hostB2 ..} .

the LUN was then shared across, and vmware volume, VMFS and data store was created on the top of the LUN. then

multiple vm was created ( on each cluster) using the the data store that is shared.

I'm wondering what would be the implication when the LUN is shared across two ESX clusters.( not within the ESX cluster)

My first thought is this may likely to cause data corruption.( I'm aware VMFS is cluster files system WITHIN the cluster)

But vmware admins insist it is safe and ESX will somehow "coordinate" the  disk access across the cluster.  Anyway, this

setup appear works for a while, until they are having a mysterious slow disk performance issue.

since vmware's VM data access is accessing individual VMDK files that reside on the share VMFS data store, I thought MAYBE it

does allow this kind of setup.    I haven't been able to find any vmware documentation either support or against sharing LUN across cluster.

Any thought , experience or advise is much appreciated.

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6 Thallium

Re: sharing a LUN across multi vmware ESX clusters?

yep, the magic sauce is VMFS, locking is done at file system level so it does not matter if ESX hosts are part of one or multiple clusters. You have to look at LUN performance stats and figure out if it's the cause of their "slowness". If you are on vSphere 4.1 and VMAX code 75 ..you might want to look at enabling VAAI to improve certain task.


1 Copper

Re: sharing a LUN across multi vmware ESX clusters?

Thanks for pointing me the right direction.

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