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From John Kinsella <...@stratosec.co>
Subject Re: Questions about KVM storage backends and resize/migrations
Date Sat, 16 Feb 2013 17:36:33 GMT
Bryan - are you running the KVM disks with writethrough or writeback caching? From my exp,
I had to switch to writethrough for gluster to work, and that resulted in a 4x performance
hit for a VM to write to the gluster store vs writing to gluster directly on the host...

John

On Feb 7, 2013, at 1:28 PM, Bryan Whitehead <driver@megahappy.net> wrote:

> I'm currently using glusterfs as a SharedMountPoint with great success.
> I've had server failures and HA smoothly powered up VM's that got hit
> without a hitch. (Each VM host has about ~4TB contributing to a volume with
> replica=2). I've also been able to migrate VM's around for maintenance on
> specific hosts.
> 
> NOTE: I have an infinband/IPoIB interconnect so glusterfs has all the IO it
> needs. I easily can push 130MB/sec write speeds inside a VM with kvm/qcow2
> backed setup.
> 
> 
> On Wed, Feb 6, 2013 at 12:55 PM, Nux! <nux@li.nux.ro> wrote:
> 
>> On 06.02.2013 19:55, Chris Sears wrote:
>> 
>>> 
>>> I'm not sure anyone could give you a "recommended" option for primary
>>> storage without knowing more about your requirements and environment,
>>> but NFS seems to be fairly common for production usage. For KVM, your
>>> storage options are NFS, RDB, CLVM, or SharedMountPoint (which could
>>> be any shared file system, eg GFS).
>>> 
>> 
>> Thanks, CLVM looks really neat and I imagine the snapshotting is also
>> superior to what we can see today with kvm+qcow2. I guess I could also use
>> Glusterfs as SharedMountPoint.
>> 
>> 
>> 
>>> Yes, CS can resize volumes, but it doesn't do anything inside the
>>> guest to resize the local filesystem/partitions.
>>> 
>> 
>> That's fair enough.
>> 
>> 
>> 
>>> If the requested resize needs more resources than the current physical
>>>> host
>>>> can provide, can CS (live) migrate the VM to another one?
>>>> 
>>> 
>>> I'm not aware of any such automatic migration feature. Most of the
>>> primary storage options would expose the same shares/LUNs to all the
>>> hosts in a cluster, so I'm not sure how often this would come up.
>>> 
>> 
>> In my case the local storage is significantly faster than anything
>> "shared" I could come up with so this feature is quite appealing. The other
>> competition's stack can do this and I wondered if cloudstack can also do
>> it. But CLVM might be a decent compromise, remains to be seen.
>> 
>> Thanks a lot!
>> 
>> 
>> Lucian
>> 
>> 
>> --
>> Sent from the Delta quadrant using Borg technology!
>> 
>> Nux!
>> www.nux.ro
>> 

Stratosec - Secure Infrastructure as a Service
o: 415.315.9385
@johnlkinsella


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