[Gluster-users] Gluster Virtual Appliance

[Brian Candler]

On Sun, Feb 24, 2013 at 12:52:53PM +0100, Gandalf Corvotempesta wrote:
> Recap: 4 phisical nodes, each node will host at least 10 VM plus 1 gluster VM
> Each VM should boot from the gluster VM

By "boot from" I guess you mean that the VM's root device, e.g. hda/vda,
will be a disk image file stored on the gluster filesystem?

> Do you have any advice on this configuration?

Yes: test it carefully to ensure it does what you want.

* In my experience, write performance of KVM -> FUSE mount -> gluster is
very poor (I was getting about 6MB/s).  In your case you have another layer
of KVM in this too.

* Test carefully all the various failure scenarios, e.g. halting and
restarting the gluster VMs, rebooting the whole server, pulling the power
out of the whole server and restarting it.  Better to learn the failure
scenarios here than when in production, because Gluster has precious little
documentation on how to cope with them.

If the *only* thing you need to do is provide backing storage for VMs, then
there are other solutions which might suit you better - you could look at
Ganeti and Sheepdog.

Ganeti uses LVM to create storage volumes for each VM and then creates DRBD
instances on top of them to synchronise replicas between hosts.  It provides
a full VM cluster manager too, so the command line lets you manage all your
VMs from one point.

Sheepdog provides a virtual block-storage layer for KVM, where chunks of
each volume are distributed and replicated between hosts.

However, neither provides a general-purpose shared filesystem as Gluster
does.

Regards,

Brian.