<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Nov 23, 2017 at 1:43 PM, Jiří Sléžka <span dir="ltr"><<a href="mailto:jiri.slezka@slu.cz" target="_blank">jiri.slezka@slu.cz</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">well, another idea<br>
<br>
when I did not use the direct flag, the performace was much better<br>
<br>
15787360256 bytes (16 GB) copied, 422.955159 s, 37.3 MB/s<br></blockquote><div><br></div><div>That means you were hitting the cache.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
probably qemu-img uses direct write too and I understand why. But in<br>
case of backup it is not as hot I think. Is there a chance to modify<br>
this behavior for backup case? Is it a good idea? Should I fill RFE?<br></blockquote><div><br></div><div>Probably not. We really prefer direct IO to ensure data is consistent.</div><div>Y.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
Cheers,<br>
<br>
Jiri<br>
<div><div class="h5"><br>
<br>
On 11/23/2017 12:26 PM, Jiří Sléžka wrote:<br>
> Hi,<br>
><br>
> On 11/22/2017 07:30 PM, Nir Soffer wrote:<br>
>> On Mon, Nov 20, 2017 at 5:22 PM Jiří Sléžka <<a href="mailto:jiri.slezka@slu.cz">jiri.slezka@slu.cz</a><br>
>> <mailto:<a href="mailto:jiri.slezka@slu.cz">jiri.slezka@slu.cz</a>>> wrote:<br>
>><br>
>> Hi,<br>
>><br>
>> I am trying realize why is exporting of vm to export storage on<br>
>> glusterfs such slow.<br>
>><br>
>> I am using oVirt and RHV, both instalations on version 4.1.7.<br>
>><br>
>> Hosts have dedicated nics for rhevm network - 1gbps, data storage itself<br>
>> is on FC.<br>
>><br>
>> GlusterFS cluster lives separate on 4 dedicated hosts. It has slow disks<br>
>> but I can achieve about 200-400mbit throughput in other applications (we<br>
>> are using it for "cold" data, backups mostly).<br>
>><br>
>> I am using this glusterfs cluster as backend for export storage. When I<br>
>> am exporting vm I can see only about 60-80mbit throughput.<br>
>><br>
>> What could be the bottleneck here?<br>
>><br>
>> Could it be qemu-img utility?<br>
>><br>
>> vdsm 97739 0.3 0.0 354212 29148 ? S<l 15:43 0:06<br>
>> /usr/bin/qemu-img convert -p -t none -T none -f raw<br>
>> /rhev/data-center/2ff6d0ee-<wbr>a10b-473d-b77c-be9149945f5f/<wbr>ff3cd56a-1005-4426-8137-<wbr>8f422c0b47c1/images/ba42cbcc-<wbr>c068-4df8-af3d-00f2077b1e27/<wbr>c57acd5f-d6cf-48cc-ad0c-<wbr>4a7d979c0c1e<br>
>> -O raw<br>
>> /rhev/data-center/mnt/<wbr>glusterSD/10.20.30.41:_rhv__<wbr>export/81094499-a392-4ea2-<wbr>b081-7c6288fbb636/images/<wbr>ba42cbcc-c068-4df8-af3d-<wbr>00f2077b1e27/c57acd5f-d6cf-<wbr>48cc-ad0c-4a7d979c0c1e<br>
>><br>
>> Any idea how to make it work faster or what throughput should I<br>
>> expected?<br>
>><br>
>><br>
>> gluster storage operations are using fuse mount - so every write:<br>
>> - travel to the kernel<br>
>> - travel back to the gluster fuse helper process<br>
>> - travel to all 3 replicas - replication is done on client side<br>
>> - return to kernel when all writes succeeded<br>
>> - return to caller<br>
>><br>
>> So gluster will never set any speed record.<br>
>><br>
>> Additionally, you are copying from raw lv on FC - qemu-img cannot do<br>
>> anything<br>
>> smart and avoid copying unused clusters. Instead if copies gigabytes of<br>
>> zeros<br>
>> from FC.<br>
><br>
> ok, it does make sense<br>
><br>
>> However 7.5-10 MiB/s sounds too slow.<br>
>><br>
>> I would try to test with dd - how much time it takes to copy<br>
>> the same image from FC to your gluster storage?<br>
>><br>
>> dd<br>
>> if=/rhev/data-center/2ff6d0ee-<wbr>a10b-473d-b77c-be9149945f5f/<wbr>ff3cd56a-1005-4426-8137-<wbr>8f422c0b47c1/images/ba42cbcc-<wbr>c068-4df8-af3d-00f2077b1e27/<wbr>c57acd5f-d6cf-48cc-ad0c-<wbr>4a7d979c0c1e<br>
>> of=/rhev/data-center/mnt/<wbr>glusterSD/10.20.30.41:_rhv__<wbr>export/81094499-a392-4ea2-<wbr>b081-7c6288fbb636/__test__<br>
>> bs=8M oflag=direct status=progress<br>
><br>
> unfrotunately dd performs the same<br>
><br>
> 1778384896 bytes (1.8 GB) copied, 198.565265 s, 9.0 MB/s<br>
><br>
><br>
>> If dd can do this faster, please ask on qemu-discuss mailing list:<br>
>> <a href="https://lists.nongnu.org/mailman/listinfo/qemu-discuss" rel="noreferrer" target="_blank">https://lists.nongnu.org/<wbr>mailman/listinfo/qemu-discuss</a><br>
>><br>
>> If both give similar results, I think asking in gluster mailing list<br>
>> about this can help. Maybe your gluster setup can be optimized.<br>
><br>
> ok, this is definitly on the gluster side. Thanks for your guidance.<br>
><br>
> I will investigate the gluster side and also will try Export on NFS share.<br>
><br>
> Cheers,<br>
><br>
> Jiri<br>
><br>
><br>
>><br>
>> Nir<br>
>> <br>
>><br>
>><br>
>> Cheers,<br>
>><br>
>> Jiri<br>
>><br>
>><br>
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