Shared Storage Devices

Question

I just had a meeting with my team, and I was trying to talk to them about masking LUNs to VMware ESX hosts in different clusters. I was trying to explain to them the risk of data corruption when two servers not joined by a cluster have access to the same LUN. They are insistent that there is no risk, and that is perfectly fine, supported, and even commonplace to share LUNs with hosts that are not in the same cluster.

Can the community help me with this? Am I being too cautious, or is there some risk involved?

Thanks!

dynamox · Answer

VMFS file system is cluster aware, it handles locking of vmdk files not the actual esx nodes in the cluster.

dynamox · Answer

it's not aware of other hosts but it handles file locking internally,  other ESX hosts would not be able to start the VM if it's already running on other host.  I have two stand-alone ESXi servers (the free version) and both are connected to one LUN from VNX, each server is running a couple of VMs from the same LUN.

kelleg · Answer

So, if you have two ESXX hosts not in a cluster configuration and both of these hosts (in different Storage Groups) share the same LUNs, that the file system will be aware of the other host? glen

Vinn2 · Answer

What I'm looking for is documentation that supports either argument. Either

a) presenting a LUN to several hosts that are not clustered together is perfectly fine, supported, and normal or

b) it should work fine, but it is not best practice, not recommended, and not supported by VMware.

Thanks!

dynamox · Answer

i don't think i have seen anything official. Do they  need to this configuration for some kind of migration ?

Storagesavvy · Answer

VMFS is a cluster file system designed to support up to 32 hosts with simultaneous access.. Each host issues locks to the files they are operating on individually and the other hosts see/respect those locks through their own view of the filesystem.

VMWare clusters are not based on the filesystem and are actually only created to put boundaries on VMWare HA and VMWare DRS and other VM availability features. There is no requirement to have a host cluster when sharing VMFS volumes, as long as the limitations of VMFS are respected (maximum number of hosts, etc)

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Shared Storage Devices

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