[Gluster-users] Gluster v 3.3 with KVM and High Availability

Mark Nipper nipsy at bitgnome.net
Thu Jul 12 09:12:31 UTC 2012

On 12 Jul 2012, Fernando Frediani (Qube) wrote:
> Gluster is not ready to run Virtual Machines at all. Yes you can build a 2 node cluster and live migrate machines, but the performance is poor and they need to do a lot of work on it yet.
> I wouldn't put in production even a cluster with low performance web server VMs until this is solved. For Archive or Multimedia general storage maybe, but not to run VMs.
> Perhaps someone is intending to integrate with RHEV (seems they are as it's going to be on oVirt 3.1 now) so they will put more effort to solve this problem that 10 of 10 of those who tested  are reporting the same thing.

	I realize that this is a major new release, so buyer
beware and all that.  But I'm actually very happy with the
performance so far.  Pretty much none of our VM's are very heavy
weight from a disk perspective.  And anything that requires a
massive amount of storage is using separate systems via NFS or
iSCSI, and not the underlying Gluster file system which only
contains the VM images themselves.  So usually active services
are all cached in RAM for the most part anyway while these VM's
are running.

	It could certainly lend itself to a perfect storm of
sorts if all the VM's suddenly start thrashing their OS disk
doing updates for example.  But we can stagger that easily enough
to avoid it.

	My only concern is whether using the writethrough cache
mode is actually considered safe by people in the know around
here.  Gluster is sufficiently magical (and this particular
release is sufficiently new) enough that everything is a moving
target right now.  Especially with Red Hat themselves busily
backporting functionality from 3.x kernels and newer versions of
libvirt and KVM/qemu into RHEL 6.x (for those of us using it) to
gain all of these whizbang features now as opposed to waiting
forever for RHEL 7.  That unfortunately means that rebooting to a
new kernel version or updating a few key packages can also
fundamentally change a previously stable and working setup into a
nightmarish house of cards just waiting to collapse.

Mark Nipper
nipsy at bitgnome.net (XMPP)
+1 979 575 3193
"If Pac-Man had affected us as kids, we'd all be running around
in dark rooms, munching pills and listening to repetitive
electronic music."
 -- Marcus Brigstocke, British comedian

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