well, another idea when I did not use the direct flag, the performace was much better
15787360256 bytes (16 GB) copied, 422.955159 s, 37.3 MB/s probably qemu-img uses direct write too and I understand why. But in case of backup it is not as hot I think. Is there a chance to modify this behavior for backup case? Is it a good idea? Should I fill RFE? Cheers, Jiri On 11/23/2017 12:26 PM, Jiří Sléžka wrote: > Hi, > > On 11/22/2017 07:30 PM, Nir Soffer wrote: >> On Mon, Nov 20, 2017 at 5:22 PM Jiří Sléžka <jiri.sle...@slu.cz >> <mailto:jiri.sle...@slu.cz>> wrote: >> >> Hi, >> >> I am trying realize why is exporting of vm to export storage on >> glusterfs such slow. >> >> I am using oVirt and RHV, both instalations on version 4.1.7. >> >> Hosts have dedicated nics for rhevm network - 1gbps, data storage itself >> is on FC. >> >> GlusterFS cluster lives separate on 4 dedicated hosts. It has slow disks >> but I can achieve about 200-400mbit throughput in other applications (we >> are using it for "cold" data, backups mostly). >> >> I am using this glusterfs cluster as backend for export storage. When I >> am exporting vm I can see only about 60-80mbit throughput. >> >> What could be the bottleneck here? >> >> Could it be qemu-img utility? >> >> vdsm 97739 0.3 0.0 354212 29148 ? S<l 15:43 0:06 >> /usr/bin/qemu-img convert -p -t none -T none -f raw >> >> /rhev/data-center/2ff6d0ee-a10b-473d-b77c-be9149945f5f/ff3cd56a-1005-4426-8137-8f422c0b47c1/images/ba42cbcc-c068-4df8-af3d-00f2077b1e27/c57acd5f-d6cf-48cc-ad0c-4a7d979c0c1e >> -O raw >> >> /rhev/data-center/mnt/glusterSD/10.20.30.41:_rhv__export/81094499-a392-4ea2-b081-7c6288fbb636/images/ba42cbcc-c068-4df8-af3d-00f2077b1e27/c57acd5f-d6cf-48cc-ad0c-4a7d979c0c1e >> >> Any idea how to make it work faster or what throughput should I >> expected? >> >> >> 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 >> >> So gluster will never set any speed record. >> >> 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. >> >> I would try to test with dd - how much time it takes to copy >> the same image from FC to your gluster storage? >> >> dd >> if=/rhev/data-center/2ff6d0ee-a10b-473d-b77c-be9149945f5f/ff3cd56a-1005-4426-8137-8f422c0b47c1/images/ba42cbcc-c068-4df8-af3d-00f2077b1e27/c57acd5f-d6cf-48cc-ad0c-4a7d979c0c1e >> of=/rhev/data-center/mnt/glusterSD/10.20.30.41:_rhv__export/81094499-a392-4ea2-b081-7c6288fbb636/__test__ >> bs=8M oflag=direct status=progress > > 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 >> >> 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. > > Cheers, > > Jiri > > >> >> Nir >> >> >> >> Cheers, >> >> Jiri >> >> >> _______________________________________________ >> Users mailing list >> Users@ovirt.org <mailto:Users@ovirt.org> >> http://lists.ovirt.org/mailman/listinfo/users >> > > > > > _______________________________________________ > Users mailing list > Users@ovirt.org > http://lists.ovirt.org/mailman/listinfo/users >
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