Just a little catch-up. This time I was able to resolve the issue by doing:
virsh blockjob domain hda --abort
virsh blockcommit domain hda --active --pivot
Last time I had to shut down the virtual machine and do this while being
offline.
Thanks Wang for your valuable input. As far as the memory goes, there's
plenty of head room:
$ free -h
total used free shared buff/cache
available
Mem: 7.8G 1.8G 407M 9.7M 5.5G
5.5G
Swap: 8.0G 619M 7.4G
2017-07-02 10:26 GMT+02:00 王李明 <wan...@certusnet.com.cn>:
> mybe this is because you physic host memory is small
>
> then this will Causing instability of the virtual machine
>
> But I'm just guessing
>
> You can try to increase your memory
>
>
>
>
>
> Wang Liming
>
>
>
>
>
> *发件人:* libvirt-users-boun...@redhat.com [mailto:libvirt-users-bounces@
> redhat.com] *代表 *Dominik Psenner
> *发送时间:* 2017年7月2日 16:22
> *收件人:* libvirt-users@redhat.com
> *主题:* Re: [libvirt-users] virtual drive performance
>
>
>
> Hi again,
>
> just today an issue I've thought to be resolved popped up again. We backup
> the machine by doing:
>
> virsh snapshot-create-as --domain domain --name backup --no-metadata
> --atomic --disk-only --diskspec hda,snapshot=external
>
> # backup hda.qcow2
>
> virsh blockcommit domain hda --active --pivot
>
> Every now and then this process fails with the following error message:
>
> error: failed to pivot job for disk hda
> error: block copy still active: disk 'hda' not ready for pivot yet
> Could not merge changes for disk hda of domain. VM may be in invalid state.
>
> I expect live backups are a great asset and should work. Is this a bug
> that may relates also to the virtual drive performance issues we observe?
>
> Cheers
>
>
>
> 2017-07-02 10:10 GMT+02:00 Dominik Psenner <dpsen...@gmail.com>:
>
> Hi
>
> a small update on this. I just migrated the vm from the site to my laptop
> and fired it up. The exact same xml configuration (except file paths and
> such) starts up and bursts with 50Mb/s to 115Mb/s in the guest. This allows
> only one reasonable answer: the cpu on my laptop is somehow better suited
> to emulate IO than the CPU built into the host on site. The host there is a
> HP proliant microserver gen8 with xeon processor. But the processor there
> is also never capped at 100% when the guest copies files.
>
> I just ran another test by copying a 3Gb large file on the guest. What I
> can observe on my computer is that the copy process is not at a constant
> rate but rather starts with 90Mb/s, then drops down to 30Mb/s, goes up to
> 70Mb/s, drops down to 1Mb/s, goes up to 75Mb/s, drops to 1Mb/s, goes up to
> 55Mb/s and the pattern continues. Please note that the drive is still
> configured as:
>
> <driver name='qemu' type='qcow2' cache='none' io='threads'/>
>
> and I would expect a constant rate that is either high or low since there
> is no caching involved and the underlying hard drive is a samsung ssd evo
> 850. To have an idea how fast that drive is on my laptop:
>
> $ dd if=/dev/zero of=testfile bs=1M count=1000 oflag=direct
> 1000+0 records in
> 1000+0 records out
> 1048576000 bytes (1.0 GB, 1000 MiB) copied, 2.47301 s, 424 MB/s
>
>
>
> I can further observe that the smaller the saved chunks are the slower the
> overall performance is:
>
> dd if=/dev/zero of=testfile bs=512K count=1000 oflag=direct
> 1000+0 records in
> 1000+0 records out
> 524288000 bytes (524 MB, 500 MiB) copied, 1.34874 s, 389 MB/s
>
> $ dd if=/dev/zero of=testfile bs=5K count=1000 oflag=direct
> 1000+0 records in
> 1000+0 records out
> 5120000 bytes (5.1 MB, 4.9 MiB) copied, 0.105109 s, 48.7 MB/s
>
> $ dd if=/dev/zero of=testfile bs=1K count=10000 oflag=direct
> 10000+0 records in
> 10000+0 records out
> 10240000 bytes (10 MB, 9.8 MiB) copied, 0.668438 s, 15.3 MB/s
>
> $ dd if=/dev/zero of=testfile bs=512 count=20000 oflag=direct
> 20000+0 records in
> 20000+0 records out
> 10240000 bytes (10 MB, 9.8 MiB) copied, 1.10964 s, 9.2 MB/s
>
> Could this be a limiting factor? Does qemu/kvm do many many writes of just
> a few bytes?
>
>
> Ideas, anyone?
>
> Cheers
>
>
>
> 2017-06-21 20:46 GMT+02:00 Dan <srwx4...@gmail.com>:
>
> On Tue, Jun 20, 2017 at 04:24:32PM +0200, Gianluca Cecchi wrote:
> > On Tue, Jun 20, 2017 at 3:38 PM, Dominik Psenner <dpsen...@gmail.com>
> wrote:
> >
> > >
> > > to the following:
> > >
> > > <disk type='file' device='disk'>
> > > <driver name='qemu' type='qcow2' cache='none'/>
> > > <source file='/var/data/virtuals/machines/windows-server-2016-
> > > x64/image.qcow2'/>
> > > <backingStore/>
> > > <target dev='hda' bus='scsi'/>
> > > <address type='drive' controller='0' bus='0' target='0' unit='0'/>
> > > </disk>
> > >
> > > Do you see any gotchas in this configuration that could prevent the
> > > virtualized guest to power on and boot up?
> > >
> > >
> > When I configure like this, from a linux guest point of view I get this
> > Symbios Logic SCSI Controller:
> > 00:08.0 SCSI storage controller: LSI Logic / Symbios Logic 53c895a
> >
> > But htis is true only if you add the SCSI controller too, not only the
> disk
> > definition.
> > In my case
> >
> > <controller type='scsi' index='0'>
> > <address type='pci' domain='0x0000' bus='0x00' slot='0x08'
> > function='0x0'/>
> > </controller>
> >
> > Note the slot='0x08' that is reflected into the first field of lspci
> inside
> > my linux guest.
> > So between your controllers you have to add the SCSI one
> >
> > In my case (Fedora 25 with virt-manager-1.4.1-2.fc25.noarch,
> > qemu-kvm-2.7.1-6.fc25.x86_64, libvirt-2.2.1-2.fc25.x86_64) with "Disk
> bus"
> > set as SCSI in virt-manager, the xml defintiion for the guest is
> > automatically updated with the controller if not existent yet.
> > And the disk definition sections is like this:
> >
> > <disk type='file' device='disk'>
> > <driver name='qemu' type='qcow2'/>
> > <source file='/var/lib/libvirt/images/slaxsmall.qcow2'/>
> > <target dev='sda' bus='scsi'/>
> > <boot order='1'/>
> > <address type='drive' controller='0' bus='0' target='0' unit='0'/>
> > </disk>
> >
> > So I think you should set dev='sda' and not 'hda' in your xml for it
> >
>
> I am actually very curious to know if that would make a difference. I
> don't have a such windows vm images ready to test at present.
>
> Dan
> > I don't kknow if w2016 contains the symbios logic drivers already
> > installed, so that a "simple" reboot could imply an automatic
> > reconfiguration of the guest....
> > Note also that in Windows when the hw configuration is considered heavily
> > changed, you could be asked to register again (I don't think that the IDE
> > --> SCSI should imply it...)
> >
> > Gianluca
>
> > _______________________________________________
> > libvirt-users mailing list
> > libvirt-users@redhat.com
> > https://www.redhat.com/mailman/listinfo/libvirt-users
>
>
>
>
> --
>
> Dominik Psenner
>
>
>
>
> --
>
> Dominik Psenner
>
--
Dominik Psenner
_______________________________________________
libvirt-users mailing list
libvirt-users@redhat.com
https://www.redhat.com/mailman/listinfo/libvirt-users
