4:47 a.m.
Hello Nir
Thanks for the advice using dd.
I found the main reason for the low level of performance.
The problem was in the faulty battery from cache-module on the disk shelf.
We also used a low-performance RAID configuration.
Thanks for the help.
05.08.2018, 18:38, "Nir Soffer" <nsoffer(a)redhat.com>:
> On Fri, Aug 3, 2018 at 12:12 PM <Aleksey.I.Maksimov(a)yandex.ru> wrote:
>> Hello
>>
>> I deployed a dedicated server (fs05.holding.com) on CentOS 7.5 and created a VDO
volume on it.
>> The local write test in the VDO volume on this server gives us an acceptable
result
>>
>> # dd if=/dev/zero of=/mnt/vdo-vd1/nfs/testfile count=1000000
>> 1000000+0 records in
>> 1000000+0 records out
>> 512000000 bytes (512 MB) copied, 6.26545 s, 81.7 MB/s
>
> This is not a good test for copying images:
> - You are not using direct I/O, and
> - You are using block size of 512 bytes, way too small
> - You don't sync at the end of the transfer
> - You don't copy real image, reading zeros does not take any time, while
> reading real image takes time. This can drop dd performance in half
>
> A better way to test this is:
>
> dd if=/path/to/src of=/path/to/dst bs=8M count=1280 iflag=direct oflag=direct
conv=fsync status=progress
>
> This does not optimize copying sparse parts of the image. For this you can use
> qemu-img, what oVirt is using.
>
> The command oVirt uses is:
>
> qemu-img convert -p -f raw|qcow2 -O raw|qcow2 -t none -T none /paht/to/src
/path/to/dst
>
>> The disk capacity of the VDO volume is connected to the oVirt 4.2.5 cluster as
the Export Domain via NFS.
>>
>> I'm seeing a problem with the low performance of Export Domain.
>> Snapshots of virtual machines are copied very slowly to the Export Domain,
approximately 6-8 MB/s.
>
> This is very very low throughput.
>
> Can you give more details on
> - the source domain, how it is connected (iSCSI/FC)?
> - the destination domain, how is it connected? (NFS 4.2?, 1G nic? 10G nic?)
> - the source image - can you attach output of:
> qemu-img map --output json /path/to/src
> - If the source image is on block storage, please copy it to a file system
> supporting sparsness using NFS 4.2 using:
> qemu-img convert -p -f raw -O raw -t none -T none /path/to/src/ /path/to/dst
> (if the image is qcow2, replace "raw" with "qcow2")
>
>> At the same time, if I try to run a write test in an mounted NFS-directory on any
of the oVit cluster hosts, I get about 50-70 MB/s.
>>
>> # dd if=/dev/zero
of=/rhev/data-center/mnt/fs05.holding.com:_mnt_vdo-vd1_nfs_ovirt-vm-backup/testfile
count=10000000
>> 10000000+0 records in
>> 10000000+0 records out
>> 5120000000 bytes (5.1 GB) copied, 69.5506 s, 73.6 MB/s
>
> Again, not a good way to test.
>
> This sounds like https://bugzilla.redhat.com/1511891.
> (the bug may be private)
>
> Finally, can you provide detailed commands to reproduce your
> setup, so we can reproduce it in the lab?
> - how to create the vdo volume
> - how you created the file system on this volume
> - NFS version/configuration on the server
> - info about the server
> - info abut the network
> - info about the host
>
> Nir