SAN Migration and VMware issues
The scenario is the following:
– SAN migration from an old EMC Clariion CX-500 to a new CX3-40
– Several Vmware ESX 3.x nodes all with 2 HBAs
The goal is to migrate all the VMware LUNs to the new SAN using EMC SAN Copy.
All the host will be powered off (yes we can live with this…).
The main issue is that when we connect the ESX host to the new SAN, the ESX hosts will see all the LUN as snapshots and will disable access.
The message in /var/log/vmkernel should be similar to this:
Jul 1 12:58:59 esxnode00 vmkernel: 0:01:00:22.568 cpu15:1045)ALERT: \ LVM: 4903: vmhba2:0:6:1 may be snapshot: disabling access. \ See resignaturing section in SAN config guide.
This seems to be the Right Way to solve the problem:
- Be sure that only 1 node has access to the LUN and no other node is writing to the LUN involved
- From 1 node, in the Advanced Settings enable LVM.EnableResignature
- Rescan all HBA
- All the LUN will be renamed to /vmfs/volumes/snap-NNNNNNNN-ORIGNAME
- Reset LVM.EnableResignature to 0 (this is REALLY IMPORTANT, you risk to get corrupted VMFS data)
- You have to register again all the VM since the UUID is changed
You can also use the option AllowSnapshot, but in this way you will keep the old UUID, and I dont like this; I think that this option should be used on a DR site.
A really interesting document (PPT) about all this is here.