Re: Question about VirtIO on Xen - Disk performance issues

[Luca Tongiani <luca.tongiani@sinte.net>]

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Hi,
Thanks for the hints , I did experiment with the changes you suggested 
and now we were able to achieve the following result : the performance 
of the domU is 50 % of the dom0 .

Is it possible to improve these numbers more ?

Also , do you have any advice on where to find extensive documentation 
on how to use Xen ?

Thank you

Luca

Il 05/01/2016 15:05, Stefano Stabellini ha scritto:
> There are a few issues in the config files. In conf_DomU_WindowsHVM:
>
> - device_model is set to /usr/lib64/xen/bin/qemu-dm, which is the old
>    qemu-xen-traditional device model, known to have worse disk
>    performance. Just delete this line to use the newer QEMU based tree.
> - disk is set to [ '/dev/vg0/winvirtio,raw,xvda1,rw' ], but you cannot
>    expose only a partition of a disk to a Windows HVM domain. The correct
>    disk line would be: disk = [ '/dev/vg0/winvirtio,raw,hda,rw' ]
>
> In conf_DomU_Xen:
>
> - you are missing builder="hvm", which means you are using a PV guest
>    rather than an HVM guest. PV guests tends to be slower on new
>    hardware.
>
> What version of Xen are you using?
>
>
> On Tue, 5 Jan 2016, Luca Tongiani wrote:
>> Sorry but I sent these logs because I have no longer available the Virtualizer of Windows DomU .
>> In any case the problem of the performance of disks is present both in the case of Linux machines PV and Windows
>> machines HVM .
>> I attach the complete log of the server and the conf of my HVM Windows Machine.
>>
>> Thanks again
>>
>>
>> Il 05/01/2016 13:42, Stefano Stabellini ha scritto:
>>
>> The xenstore-ls output is not complete. Could you please send it again?
>>
>> I noticed from the DomU config file that it is not a Windows VM, as
>> previously discussed, but a Linux VM. That is OK, but of course in that
>> case you won't be able to use the Windows PV drivers which I linked.
>> Linux has its own set of drivers. Did you enable the Xen PV frontends in
>> the Linux kernel you use (/var/xen/boot/vmlinuz-4.0.5-gentoo_bmsbackup)?
>> Did you compile them a built-in or as modules?
>>
>> On Tue, 5 Jan 2016, Luca Tongiani wrote:
>>
>> Hi,
>> thanks in advance for your reply :)
>>
>>
>> I have attached the following email configuration DomU and the output you have requested .
>> Performance disk are all my machines the most serious problem , even if they are used powerful hardware .
>> Differences in Disk writing in DomU are 1/3 of those of the Dom0 .
>>
>>
>> Thank you in advance Luca
>>
>>
>>
>>
>>
>>
>>
>> Il 05/01/2016 12:09, Stefano Stabellini ha scritto:
>>
>> Could you please post your VM config file and the output of
>> xenstore-ls once the VM has completed the boot sequence?
>>
>> On Tue, 5 Jan 2016, Luca Tongiani wrote:
>>
>> Hi Stefano,
>> im writing to you because im having issue with I/O disk in my DomU With Xen (Gentoo based system).
>>
>> I tried to use the driver that you provided for the PV .
>> But the results are still not good , there is no way to support the use of Xen VirtIO disk ? Many thanks in
>> advance
>>
>> Luca
>>
>> Il 12/16/15 12:31, Stefano Stabellini ha scritto:
>>
>> Hello Luca,
>>
>> the recommended way to increase disk performance would be to use Xen PV
>> disks. You just need to install the Windows PV drivers:
>>
>> http://www.xenproject.org/developers/teams/windows-pv-drivers.html
>>
>> But using VirtIO disk should also increase performance, even though
>> most probably not as much.
>>
>> Cheers,
>>
>> Stefano
>>
>> On Tue, 15 Dec 2015, Luca Tongiani wrote:
>>
>> Hi to all,
>> I'm writing you this mail for asking some advice about a great problem i'm havin in running a Windows VM
>> (HVM) onto a Xen (Gentoo based) Hypevisor.
>>
>> I need to achieve maximum performance from this VM because of intense SQL tasks running in it.
>>
>> I've seen good improvement in IO on disk using VirtIO on a Windows VM onto a QEMU (QNAP) hypervisor, and i'm
>> tryin to use this feature also on my Xen HV.
>> Is VirtIO disk a good way to improve performance?
>>
>> Thx in advance and hope to keep in touch
>> --
>>
>> Luca Tongiani
>>
>> Sinte srl
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>>
>>
>>
>>
>> --
>>
>> Luca Tongiani
>>
>> Sinte srl
>> Soluzioni Informatiche e Telematiche
>> via Monte Grappa 4/B
>> 20900 Monza (MB)
>>
>> Tel (+39) 039 200 59 60
>> Fax (+39) 039 200 69 42
>> Web www.sinte.net
>>
>>
>>
>>
>> --
>>
>> Luca Tongiani
>>
>> Sinte srl
>> Soluzioni Informatiche e Telematiche
>> via Monte Grappa 4/B
>> 20900 Monza (MB)
>>
>> Tel (+39) 039 200 59 60
>> Fax (+39) 039 200 69 42
>> Web www.sinte.net
>>
>>
>>
>>
>> --
>>
>> Luca Tongiani
>>
>> Sinte srl
>> Soluzioni Informatiche e Telematiche
>> via Monte Grappa 4/B
>> 20900 Monza (MB)
>>
>> Tel (+39) 039 200 59 60
>> Fax (+39) 039 200 69 42
>> Web www.sinte.net
>>
>>
>>

-- 

*Luca Tongiani*

*Sinte* srl
Soluzioni Informatiche e Telematiche
via Monte Grappa 4/B
20900 Monza (MB)

*Tel* (+39) 039 200 59 60
*Fax* (+39) 039 200 69 42
*Web* www.sinte.net <http://www.sinte.net/>


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