Re: [Xen-users] Disk starvation between DomU's

[Thanos Makatos <thanos.makatos@xxxxxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxx [mailto:xen-users-
> bounces@xxxxxxxxxxxxx] On Behalf Of Wiebe Cazemier
> Sent: 10 June 2013 09:11
> To: xen-users@xxxxxxxxxxxxx
> Subject: [Xen-users] Disk starvation between DomU's
> 
> Hi,
> 
> I have the issue of my virtual machines becoming extremely slow when
> even only one of them is creating a lot of I/O. Is there a way to
> prioritize disk access? I can't seem to find any.
> 
> The Xen host in question is:
> 
> - Quad core Xeon X3430  @ 2.40GHz
> - 3Ware 9650SE RAID6 array, Seagate 2 TB disks.
> - Xen 4.0.1-5.8 on Debian 6 (upgrade planned)
> - 15 DomU's
> - All VM's have noop as disk scheduler (cat
> /sys/block/xvda2/queue/scheduler)
> - VM's are prioritized with 'xm sched-cred', but that doesn't help the
> disk much.
> - Dom-0 has significantly more credits (10000) because it needs to
> service IO's.
> - Dom-0 doesn't do anything else.
> - All virtual disks are logical volumes, exposed to the VM through xen-
> blkfront
> 
> So, what can I do to improve disk performance or priority?

Can you try using ionice to set the disk priority of the corresponding 
tapdisk/qemu process?

> 
> Regards,
> 
> Wiebe
> 
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