Re: [ovirt-users] slow performance with export storage on glusterfs

23 Nov 2017

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Hi,

On 11/22/2017 07:30 PM, Nir Soffer wrote:
...
On Mon, Nov 20, 2017 at 5:22 PM Ji=C5=99=C3=AD Sl=C3=A9=C5=BEka <jiri.s=
lezka@slu.cz
<mailto:jiri.slezka@slu.cz>> wrote:
=20
    Hi,
=20
    I am trying realize why is exporting of vm to export storage on
    glusterfs such slow.
=20
    I am using oVirt and RHV, both instalations on version 4.1.7.
=20
    Hosts have dedicated nics for rhevm network - 1gbps, data storage i=
tself
    is on FC.
=20
    GlusterFS cluster lives separate on 4 dedicated hosts. It has slow =
disks
    but I can achieve about 200-400mbit throughput in other application=
s (we
    are using it for "cold" data, backups mostly).
=20
    I am using this glusterfs cluster as backend for export storage. Wh=
en I
    am exporting vm I can see only about 60-80mbit throughput.
=20
    What could be the bottleneck here?
=20
    Could it be qemu-img utility?
=20
    vdsm=C2=A0 =C2=A0 =C2=A0 97739=C2=A0 0.3=C2=A0 0.0 354212 29148 ?=C2=
=A0 =C2=A0 =C2=A0 =C2=A0 S<l=C2=A0 15:43=C2=A0 =C2=A00:06
    /usr/bin/qemu-img convert -p -t none -T none -f raw
    /rhev/data-center/2ff6d0ee-a10b-473d-b77c-be9149945f5f/ff3cd56a-100=
5-4426-8137-8f422c0b47c1/images/ba42cbcc-c068-4df8-af3d-00f2077b1e27/c57a=
cd5f-d6cf-48cc-ad0c-4a7d979c0c1e
    -O raw
    /rhev/data-center/mnt/glusterSD/10.20.30.41:_rhv__export/81094499-a=
392-4ea2-b081-7c6288fbb636/images/ba42cbcc-c068-4df8-af3d-00f2077b1e27/c5=
7acd5f-d6cf-48cc-ad0c-4a7d979c0c1e
=20
    Any idea how to make it work faster or what throughput should I
    expected?
=20
=20
gluster storage operations are using fuse mount - so every write:
- travel to the kernel
- travel back to the gluster fuse helper process
- travel to all 3 replicas - replication is done on client side
- return to kernel when all writes succeeded
- return to caller
=20
So gluster will never set any speed record.
=20
Additionally, you are copying from raw lv on FC - qemu-img cannot do
anything
smart and avoid copying unused clusters. Instead if copies gigabytes of=
...
zeros
from FC.
ok, it does make sense
...
However 7.5-10 MiB/s sounds too slow.
=20
I would try to test with dd - how much time it takes to copy
the same image from FC to your gluster storage?
=20
dd
if=3D/rhev/data-center/2ff6d0ee-a10b-473d-b77c-be9149945f5f/ff3cd56a-10=
05-4426-8137-8f422c0b47c1/images/ba42cbcc-c068-4df8-af3d-00f2077b1e27/c57=
acd5f-d6cf-48cc-ad0c-4a7d979c0c1e
of=3D/rhev/data-center/mnt/glusterSD/10.20.30.41:_rhv__export/81094499-=
a392-4ea2-b081-7c6288fbb636/__test__
bs=3D8M oflag=3Ddirect status=3Dprogress
unfrotunately dd performs the same

1778384896 bytes (1.8 GB) copied, 198.565265 s, 9.0 MB/s
...
If dd can do this faster, please ask on qemu-discuss mailing list:
https://lists.nongnu.org/mailman/listinfo/qemu-discuss
=20
If both give similar results, I think asking in gluster mailing list
about this can help. Maybe your gluster setup can be optimized.
ok, this is definitly on the gluster side. Thanks for your guidance.

I will investigate the gluster side and also will try Export on NFS share=
=2E

Cheers,

Jiri
...
=20
Nir
=C2=A0
=20
=20
    Cheers,
=20
    Jiri
=20
=20
    _______________________________________________
    Users mailing list
    Users@ovirt.org <mailto:Users@ovirt.org>
    http://lists.ovirt.org/mailman/listinfo/users
=20
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Re: [ovirt-users] slow performance with export storage on glusterfs

Jiří Sléžka