[ovirt-users] Live merge speed

[Markus Stockhausen]

Hi Maor,

from our observation it MIGHT come from the xfs filesystem on the NFS storage.
qemu thin provisioned raw disks of linux database VMs tend to fragment heavily
during growth. Some of the disk images have > 1.000.000 extends.

To sort it out we have fixed the extendsize of the OVirt mount point to 1M
(xfs_io -c 'extsize 1m' /var/nas/OVirt). If this does not help I will send you some
update.

Best regards.

Markus


>>>
Von: Maor Lipchuk [mlipchuk at redhat.com]
Gesendet: Sonntag, 6. November 2016 16:33
An: Markus Stockhausen
Cc: Ovirt Users
Betreff: Re: [ovirt-users] Live merge speed

Hi Markus,

Can you try to use dd on a random file in that storage domain, What is the performance it reflects? 
Just want to make sure what is the origin of the problem, if  it is related to the storage domain or the qemu process.

Regards,
Maor

On Thu, Nov 3, 2016 at 8:09 PM, Markus Stockhausen 
<stockhausen at collogia.de> wrote:

Hi there,

in the past we already observed that live merge operations may take some time.
Currently another of those operations is running on one of our VMs on a
CentOS 7/qemu 2.3 node. Storage is (async - yeah I know about potential data
loss) NFS over 10GBit network.

The operation is running for 50 minutes now with an average throughput of
5MByte/sec. The disk (defined at 400GB) and its snapshots does not show much
thin provisioning:

ls -al
-rw-rw----.   1 vdsm kvm 429496729600  7. Apr 2016  a204865e-ef57-41e0-a2ac-465a6c9c3d60
-rw-rw----.   1 vdsm kvm 203334418432  3. Nov 2016  aeda833f-1f4b-4b6f-b553-578f1f3f06ee
-rw-rw----.   1 vdsm kvm 192091389952  3. Nov 2016  c8acdbc7-af24-4c5c-94c5-ae7262d98f5c
du -m a204865e-ef57-41e0-a2ac-465a6c9c3d60
383070  a204865e-ef57-41e0-a2ac-465a6c9c3d60
du -m aeda833f-1f4b-4b6f-b553-578f1f3f06ee
193953  aeda833f-1f4b-4b6f-b553-578f1f3f06ee
du -m c8acdbc7-af24-4c5c-94c5-ae7262d98f5c
183222  c8acdbc7-af24-4c5c-94c5-ae7262d98f5c

Usually at some point the process is gaining speed and we see >100MByte/sec
speed. Can anyone explain what might be going on.

Best regards.

Markus Stockhausen
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