Power savings through virtualization

As we finally shut down our old SAN we were able to see the effect of virtualization on our power consumption today and we were quite amazed by the results. So far, 33% into our project, we have been able to reduce our power requirement in datacenter 1 by 3.7 KiloWatts (18.7 down to 15.0) and in datacenter 2 by approximately 1.5 KiloWatts. Unfortunately I am not able to calculate a true cost savings from this as I don’t have the pricing for our energy but when we finish it will be significant.

Because we are virtualizing everything to one production datacenter we will eventually be able to shut down datacenter 2 for production (which will mean less stringent requirements on cooling, UPS etc.). It will be interesting to see what the final outcome is for the project.

All is well and we still love ESX

Well, in the end it didn’t need an official response from VMware to solve the problem:

It seems that our troubleshooting efforts (rescanning, resignaturing and rebooting the servers somehow fixed the problem). We checked the /var/log/vmkernel and found that after setting LVM.EnableResignature to on and LVM.DisallowSnapshotLUN to off the host already saw the LUN’s as regular LUN’s in stead of snapshots but we weren’t able to rename them.

At first we thought the two problems to be related but this morning (after sleeping over it) we started to look in another direction and found an orphaned Shared Storage resource that probably wasn’t cleaned up correctly by ESX with the rescan of the storage.

After deleting this orphan we were able to rename all the Shared Storage resources. After a final reboot of the host all Shared Storage resources were detected as normal LUN’s so everything is fixed now. I have made a post in the VMWare forums with more details.

The fun thing this morning was that we were running full production while fixing one host. We just VMotioned everything over to the other host ! And then when we were done we just VMotioned everything back. And we had no complaints from users while doing that !

I mean, taking 40 servers down for maintenance in the middle of the morning would normally be impossible. After hating it yesterday when it was giving us problems, I am loving it today.