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sync in container [message #45153]

Thu, 02 February 2012 04:56

iowissen
Messages: 11
Registered: February 2012

Junior Member

hi all,

we found sync in container may cause high disk I/O load (not able to
supress it even with blkio throttle settings).

do anyone have the similar experience and information to share? thanks a
lot in advance.

best,
maoke

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Re: sync in container [message #45489 is a reply to message #45153]

Tue, 13 March 2012 07:24

Andrew Vagin
Messages: 28
Registered: November 2011

Junior Member

On 02/02/2012 08:56 AM, Maoke wrote:
> hi all,
>
> we found sync in container may cause high disk I/O load (not able to
> supress it even with blkio throttle settings).
Yes, it's known issue and it's, because all containers use one file
system. Below you can find a few workarounds of this problem:
* You can disable fsyncs inside the VE by writing 0 to
/proc/sys/fs/fsync-enable on the HN. This means that all fsyncs inside
VE would be very fast as fsync actually doesn't happen.
* You can mount a host file system in write-back cache mode.
* Create a container on separate lvm volume.
* Wait a bit and start to use ploop (container in a file).
http://wiki.openvz.org/Ploop
>
> do anyone have the similar experience and information to share? thanks
> a lot in advance.
>
> best,
> maoke
>
>

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Re: sync in container [message #45502 is a reply to message #45489]

Tue, 13 March 2012 10:39

Aleksandar Ivanisevic is currently offline

Aleksandar Ivanisevic
Messages: 34
Registered: April 2011

Member

Andrew Vagin <avagin@parallels.com> writes:

> * You can disable fsyncs inside the VE by writing 0 to
> /proc/sys/fs/fsync-enable on the HN. This means that all fsyncs
> inside VE would be very fast as fsync actually doesn't happen.

Are there any docs about this sysctl? I've googled and searched the
openvz wiki and all I found is the announcement that it has been added
some time in 2008 with no further explanations.

One would think that it should be pretty straightfoward; 0=off, 1=on,
but on all my systems it is set to 2 which makes me wonder if there is
more to it.

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