[Users] Storage Performance Issue !

[Ayal Baron]

----- Original Message -----
> On Wed, Feb 19, 2014 at 1:45 PM, Sven Kieske  wrote:
> > Just as a quick shot:
> >
> > You really may want to check which IO scheduler runs inside the
> > vm. you probably want deadline or noop instead of CFQ, which
> > can have a huge performance impact inside the vms.
> 
> BTW: actually I'm already doing it (setting scheduler as deadline) at
> hypervisor level for my oVirt hosts, even if it seems to me it is not
> the default...
> What do you think about it? This way a single process (aka vm) cannot
> have such huge performance impact and you have nothing to do at VM
> level...
> Even in recent fedora (19) I see some situations where cfq is
> suboptimal in case of heavy I/O operations...

1. oVirt is already setting deadline on the host for you.
2. did you install the ovirt guest agent inside your VMs? if not, you should, among other things it should configure tuned with virt-guest which sets the I/O shceduler properly
3. what interface are you using for your virtual disks? (ide / virtio-blk / virtio-scsi)  If not virtio-blk then change it.
4. If I understand correctly you're using local storage.  What file system are you using?
5. did you actually measure I/O performance at host and inside the guest to compare and see what hit you're taking?
6. do you have anything else writing to these disks? esp. if you have anything that is writing not using direct I/O you could be starving your VMs.


> 
> Gianluca
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