Remove node from cluster

[hstuivenberg]

We have a customer with a 4 node cluster of P4300's with a FOM, connected to an Hyper-V cluster and using CSV volumes with data in it.

Due to the migration of a lot of VM's from the customers site to our datacenter, we want to streamline the P4300's at the customers location: remove 2 nodes from the cluster.

Can we do that? Can we remove 2 nodes, without reconfiguring volumes or copying data from the volumes?

[Gediminas Vilutis]

If space on remaining nodes enough to accomodate existing volumes, then yes, you can edit cluster and remove 2 nodes from it.

Gediminas

[Northwoods]

Depends on how logically you want to move the data. In almost all scenarios at least one restripe will be required.

[oikjn]

removing nodes from a cluster will ALWAYS cause a restripe at the cluster level. If I understand the OP correctly, he wants to know if he'll have to change anything at the LUN level in order to allow this change. The answer for that is, as ged said, "it depends". You can remove any number of nodes you want from a cluster at any time, but you have to make sure you keep the total space of the cluster larger than the utilized space of the cluster or writes will stop on the cluster.

Simplest thing to do is check out the Cluster details page and see if the utilization is under 50%. If it is you technically CAN remove the two nodes without a problem. HOWEVER, I would imagine that the existing LUNs are thin provisions and have expanded on the cluster. I also bet that since you migrated the data off, that most of that is free space. The problem is there is currently no way to recover that space from the existing LUNs. As a result, I would suggest that before you remove the nodes, you create an additional temporary LUN to assist your shrinking of the other luns. add that new LUN as a new CSV to the cluster, migrate all of the existing VMS from one of the existing LUNs to the new LUN, then remove the existing CSV from the cluster, then shrink the volume size in disk manager, then shrink the LUN size in CMC to something a bit larger than the volume size, then expand the volume size back to its original size after you see the volume consumed space go down, then refresh the disk info and expand it back in windows and add it back to the cluster. After that, you can migrate the VMs back to that disk and repeat the process for all existing CSV volumes.

The above process is a pain in the ass, but since the SAN doesn't have a way to reclaim the "free" space in the CSV, that is the only way to shrink an expanded LUN. This is an "optional" step, but I definitely suggest using it to free up the space on the SAN before you remove half of the space.

Either way, you can remove the two nodes from the cluster as long as you are under 50% utilization, but remember that your cluster utilization will effectively double whatever it currently says... and no matter what, if you change the number of nodes in the cluster, you WILL have a cluster restripe take place.