[CentOS-virt] Can I use direct attached storage as a shared filesystem in Xen

Christopher G. Stach II cgs at ldsys.net
Tue Feb 9 17:46:11 UTC 2010

----- "Rich" <rhdyes at gmail.com> wrote:

> I think the better question is this. How can I make my 2 physical
> servers that are identical into the best clustered solution sharing
> the storage between the 2.

Do you want the storage to be redundant between the two like RAID 1 or just all of it accessible to any guest on either machine like a JBOD? For either, you can use a suitable mix of drbd, iSCSI, GNBD, LVM, heartbeat, keepalived, and a clustered filesystem. If you do the latter, remember that this squares your risk. If you want a simple A/B failover setup where the second physical host is idle until the first physical host fails, you can just use drbd and heartbeat or RHCS.

> They all use xfs.
> I want to keep the guests the same on each server.
> I will start with the backup server. I will go on each vm and delete
> this FS and block device.
> I then want make that whole 10 terabyte raid into one gfs and then
> re-attach it back to each guest.
> Is that possible or do I have to start all over again? If it can be
> done I then will sync the date from the mainserver to this backup
> server and then switch them and do the same to the mainserver.

That sounds about right. You need to make your backups (!), destroy the data on of your servers by creating the new clustered filesystem, copy the data from the other server, and then share it with your reconfigured guests. So, basically what you said.

> I have one more question which is another whole thread.
> I am using rsync to sync the 2 physical boxes now. Is there a better
> way to do this?

drbd, but rsync does a pretty good job in a lot of use cases. I wouldn't say that it fits this one, though.

Christopher G. Stach II

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