RHEVM: Shared Disks. What does it provide ?

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I have a possible use case for the new shared disk feature in 3.1 but there is little information as to what exactly it provides.

Am I right to assume it does little more than configure the disk as clustered LVM volume and makes it available to other VM's ?

I still need to put a clustered filesystem on top of it (GFS?) and create some sort of clustering mechanism (RHCS) with the ability to fence nodes , right ?

How would I fence a RHEV VM ?


Thank You


I actually have a similar need to install RHCS on top of RHEV, this would obviously include storage seen by both VMs and a quorum disk. Any info on this topic would be helpful and appreciated. 


I used that feature a lot to simulate clusters in my test RHEV setup. You are correct in your assumption; it only shares the raw disk between multiple VMs (similar to accessing a LUN from multiple machines); you'd still need to have a clustered filesystem, and, if you're using GFS2, have some fencing in place. You can use the fence_rhev script included in the High Availability add-on (fence-agents). You can test it on the command line like this:

fence_rhevm --ssl --action=status --ip=your.rhevm.machine --username=admin@internal --password=youradminpass --plug=YourVMname

Note that this may be less than ideal in production as your password is kept in plain text. You can use --password-script but I imagine it'd have to be kept in plain text somewhere. I suppose you could create a user that only has permission to control a specific VM and use that user instead.

Rizvi - Thank You !