Re: [Qemu-discuss] virtual disks perfermonca <=2MB/s

[Vincenzo Romano]

I am glad I misunderstood your report!
Someone else already suggested you to test "bare bones" disk I/O performances
--
Vincenzo Romano - NotOrAnd.IT
Information Technologies
--
NON QVIETIS MARIBVS NAVTA PERITVS


2017-02-20 14:07 GMT+01:00 Mimiko <address@hidden>:
> On 20.02.2017 13:13, Vincenzo Romano wrote:
>>
>> I could be wrong, but are you willing to run a VM with a disk image
>> over CIFS/SAMBA?
>> If not, why are you quoting your network throughput?
>
>
> No, I do not share a disk image via cifs/samba. This is a test machine,
> mostly used for compiling, and I shared / folder to browse all files.

Good. I am glad I misunderstood you.

>> Could you please try (on a separate test VM) raw and qcow2?
>
> This VM was setup 2 days ago with latest Debian updates for Jessie.
> I've created a raw disk of 10GB and attached to VM and mounted it. The speed
> is same - 2MB.

I think you have to first check your barebones disk I/O throughput.

> As per same cifs/samba access to / on the host - the speed is 180MB+, as
> there are 2 network interfaces in alb bond.

No need to take into account your network unless you're killing your system
with Gbps of sustained traffic. In that case maybe the I/O could lag a
little bit.

>> In understand your concerns about the disk space allocation, but if
>> you create a virtual disk of 50GB, I think you'd know it could grow up
>> to that size and that it won't automatically shrink back.
>
> This is my first attempt of a VM on qemu after a lot of years using Hyper-V
> 2008 R2.
> In Hyper-V I have little performance loose compared to direct host's disk
> access, and virtual disks can be compacted using gui command. I think that
> periodically I can recompact virtual disk using qemu/kvm/libvirt tools or
> Hyper-V in case of vhc/vhd (theoretically, as I've never reached initial
> limit, but I have chance to store more virtual disks for multiple VMs)

Did you get the same I/O performances on the same hardware with Hyper-V?
I suspect you are experiencing some hardware limitation: 2MBps is a
very low score,
unless the hardware is broken or really oldish.

>> Please, elaborate more on your environment and objectives.
>
> It will be for compiling and testing. Thats why I mentioned that 50MB is ok.

>
>
> On 20.02.2017 13:37, Jakob Bohm wrote:
>> What does the same test return on the host (wheezy) machine on the same
>> disk/partition as the vhd.
>
> The host can handle 180MB+
>
>> Also, consider using the native qemu disk image format (qcow2) instead
>> of the VHD format compatibility layer.
>
> I've tried raw and the speed is same.
>
>> virsh domxml-to-native qemu-argv tmp.xml
> LC_ALL=C PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
> HOME=/ QEMU_AUDIO_DRV=none /usr/bin/kvm -S -M pc-1.1 -enable-kvm -m 2048
> -smp 4,sockets=4,cores=1,threads=1 -name srv -uuid
> c23810c8-fe96-12df-5769-5a7a80c3c35f -no-user-config -nodefaults -chardev
> socket,id=charmonitor,path=/var/lib/libvirt/qemu/srv.monitor,server,nowait
> -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown
> -boot order=cn,menu=on -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2
> -drive
> file=/vdisks/root.vhd,if=none,id=drive-virtio-disk0,format=vpc,cache=writeback
> -device
> virtio-blk-pci,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0
> -netdev tap,id=hostnet0 -device
> rtl8139,netdev=hostnet0,id=net0,mac=00:00:00:00:00:00 -chardev
> pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -vnc
> 0.0.0.0:53181 -vga cirrus -device
> virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x8
>
>> /usr/bin/kvm --version
> QEMU emulator version 1.1.2 (qemu-kvm-1.1.2+dfsg-6+deb7u19, Debian),
> Copyright (c) 2003-2008 Fabrice Bellard
>
>> virsh dumpxml YOURVMNAME > tmp.xml
> <domain type='kvm' id='10'>
>   <name>srv</name>
>   <uuid>c23810c8-fe96-12df-5769-5a7a80c3c35f</uuid>
>   <memory unit='KiB'>2097152</memory>
>   <currentMemory unit='KiB'>2097152</currentMemory>
>   <vcpu placement='static'>4</vcpu>
>   <os>
>     <type arch='x86_64' machine='pc-1.1'>hvm</type>
>     <boot dev='hd'/>
>     <boot dev='network'/>
>     <bootmenu enable='yes'/>
>   </os>
>   <features>
>     <acpi/>
>     <apic/>
>     <pae/>
>   </features>
>   <clock offset='utc'/>
>   <on_poweroff>destroy</on_poweroff>
>   <on_reboot>restart</on_reboot>
>   <on_crash>restart</on_crash>
>   <devices>
>     <emulator>/usr/bin/kvm</emulator>
>     <disk type='file' device='disk'>
>       <driver name='qemu' type='vpc' cache='writeback'/>
>       <source file='/vdisks/root.vhd'/>
>       <target dev='vda' bus='virtio'/>
>       <alias name='virtio-disk0'/>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x04'
> function='0x0'/>
>     </disk>
>     <controller type='usb' index='0'>
>       <alias name='usb0'/>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x01'
> function='0x2'/>
>     </controller>
>     <interface type='bridge'>
>       <mac address='52:54:00:de:83:2d'/>
>       <source bridge='br0'/>
>       <target dev='vnet0'/>
>       <model type='virtio'/>
>       <alias name='net0'/>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x03'
> function='0x0'/>
>     </interface>
>     <serial type='pty'>
>       <source path='/dev/pts/4'/>
>       <target port='0'/>
>       <alias name='serial0'/>
>     </serial>
>     <console type='pty' tty='/dev/pts/4'>
>       <source path='/dev/pts/4'/>
>       <target type='serial' port='0'/>
>       <alias name='serial0'/>
>     </console>
>     <input type='mouse' bus='ps2'/>
>     <graphics type='vnc' port='59081' autoport='no' listen='0.0.0.0'>
>       <listen type='address' address='0.0.0.0'/>
>     </graphics>
>     <video>
>       <model type='cirrus' vram='9216' heads='1'/>
>       <alias name='video0'/>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x02'
> function='0x0'/>
>     </video>
>     <memballoon model='virtio'>
>       <alias name='balloon0'/>
>       <address type='pci' domain='0x0000' bus='0x00' slot='0x08'
> function='0x0'/>
>     </memballoon>
>   </devices>
>   <seclabel type='none'/>
> </domain>
>
>
>