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Re: Heavy Disk IO from a single VM can block the other VMs on the same host [message #44341 is a reply to message #44339]

Thu, 01 December 2011 17:27

Kirill Korotaev
Messages: 137
Registered: January 2006

Senior Member

That's most likely due to a single file system used for containers - journal becomes a bottleneck.
fsync forces journal flushes and other workloads begin to wait for journal... In reality workload looks like this are typical for
heavy loaded databases or mail systems only.

How to improve:
- increase journal size
- split file systems, i.e. run each container from it's own file system

Thanks,
Kirill

On Nov 29, 2011, at 20:13 , Hubert Krause wrote:

> Hello,
>
> my environment is a Debian squeeze host with a few debian squeeze
> guests. The private and root filesystems of the guest are locatet on
> the same raid device (raid5) in an luksCrypt Container in an LVM
> container on an ext4 partition with nodelalloc as mountoption. If I run
> the tool stress:
>
> stress --io 5 --hdd 5 --timeout 60s (which means fork 5 threads doing
> read/write access and 5 threads doing constantly fsync) the
> responsivness of the other VMs is very bad. That means, Isolation for
> IO operations is not given. I've tried to reduce the impact of the
> VM with 'vzctl set VID --ioprio=0'. There was only a
> minor effect, my application on the other VM where still not
> responsive.
>
> Any Idea how to prevent a single VM to disturb the other VMs regarding
> diskIO?
>
> Greetings
>
> Hubert

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[Message index]

		Heavy Disk IO from a single VM can block the other VMs on the same host By: Hubert Krause on Tue, 29 November 2011 16:13
		Re: Heavy Disk IO from a single VM can block the other VMs on the same host By: Bogdan-Stefan Rotariu on Thu, 01 December 2011 15:49
		Re: Heavy Disk IO from a single VM can block the other VMs on the same host By: Kirill Korotaev on Thu, 01 December 2011 17:27
		Re: Heavy Disk IO from a single VM can block the other VMs on the same host By: quantact-tim on Fri, 02 December 2011 18:18
		Re: Heavy Disk IO from a single VM can block the other VMs on the same host By: Hubert Krause on Tue, 06 December 2011 17:18

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