Share storage between host clusters

[WGSSS]

Hi,

I have a number of host clusters managed under one VC server. I want to decommission the ESX 3.5 clusters, and move all my VMs to my vSphere cluster. I plan to move the storage currently being used by the ESX 3.5 clusters as well.

Is it OK (i.e. supported) or even possible for me to do the following ?

1. Attach the storage used by the ESX 3.5 cluster to the vSphere cluster (so it is visble to BOTH clusters).

2. vMotion the servers from the ESX3.5 cluster to the vSphere cluster.

3. Decommission the ESX 3.5 cluster.

I guess this boils down to two questions.

1. Can you have storage shared between two host cluster?

2. If you can, is it possible to vMotion between host clusters, assuming that all vMotion compatibility checks are successful?

If the above is not possible, I am guessing that a V2V of the ESX 3.5 VMs would be the way forward, and I'd have to find new storage for the vSphere cluster.

Thanks,

G

[illvilja · Accepted solution]

Hi,

If you have a vSphere-supported SAN, then there is no problem.

Depending on the arch on your ESX 3.5/vSphere hosts CPU, you might have problems with storage vmotion/vmotion. One way could be to enable EVC, that however requires ALL VMs to be powered off.

But presenting the 3.5 LUNs to 4.x hosts and doing an svmotion isn't a problem if you have supported storage. (www.vmware.com/go/hcl).

Then you can just vmotion (if you don't have CPU mismatch) the VMs to the new hosts, or shut down and relocate.

VCP3/VCP4/VSP/VTSP/MCTS: Virtualization

[WGSSS]

Excellent.

Thanks for your quick response.

Cheers,

G

[f10]

Hi,

Answers to your questions:

1. Can you have storage shared between two host cluster?

Yes, because the version of VMFS remains the same, not much changes have been made in the VMFS version. You can have a datastore shared between ESX 3.5 and ESX 4.x

2. If you can, is it possible to vMotion between host clusters, assuming that all vMotion compatibility checks are successful?

Yes, if I have two clusters 1 & 2 I can vmotion a powered on VM from cluster 1 to Cluster 2(from ESX 3.5 to ESX 4). Ensure that the ESX server CPU's are compatible for vMotion.

Let me know if you have any questions

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[FirstByte]

Would you agree that sharing the same storage luns across clusters is not recommended?

Is there any documented best practices around why this type of config is preferred or not?

Example: If you have a cluster dedicated to some business application like Citrix, or Exchange - It has its own cluster, its own hosts, uses its own dedicated networks/vlans, don't you think it should also have its own set of storage luns as well? Why would you share these luns across a different cluster in your VC which might have different purpose, like general servers, or development stuff, or test or even DMZ servers? Surely that's the idea behind segregating your environment into their clusters, is to keep the load separate. The risk of damage is far higher if someone with fat fingers working on a development server on some other cluster, but that has access to the same datastore as your higher priority production app is enough to warrant splitting out storage so that each cluster has its own luns?

And advice/tips would be appreciated

Thanks

Darren

[JulieFI]

I had a similar question and verified that sharing storage across clusters is supported as long as the clusters exist in the same vCenter and Data Center.  There are some scenarios where this portability is desired.  Best practice is to manage them separately, mostly due to complexity.