[Users] Heavy Disk IO from a single VM can block the other VMs on the same host

[tim Doyle]

You can use vzctl --ioprio to set relative disk I/O priorities:
http://wiki.openvz.org/I/O_priorities_for_VE

-Tim

-- 
Timothy Doyle
CEO
Quantact Hosting Solutions, Inc.
tim at quantact.com
http://www.quantact.com


On 12/01/2011 09:27 AM, Kirill Korotaev wrote:
> 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
>> _______________________________________________
>> Users mailing list
>> Users at openvz.org
>> https://openvz.org/mailman/listinfo/users
>
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