Re: [Users] vzctl chkpnt speed

2013-01-21 Thread Stanislav Kinsbursky 

On Fre, 2013-01-18 at 16:26 +0100, Roman Haefeli wrote:

Hi all

Only recently I discovered that online migration seems to work for us
now. CT on NFS or NFS mounted inside a CT is non-issue now.

We are running all our CTs on an NFS filesystem shared between
hostnodes. While checkpointing and restoring works flawlessly with that
setup, I noticed that vzctl chkpnt CTID writes slower to the NFS mount
compared to a dd-write, for instance.

'dd if=/dev/zero of=/mnt/nfs/deleteme bs=1M' writes with approx. 70MB/s.
'iotop' shows that 'vzctl chkpnt CTID' writes with only 18MB/s to the
same dir.

However, the speed of writing is similar to the one of dd when I use the
'bs=8k' option for dd. This makes me assume that quite some write
performance could be gained, if checkpointing would write bigger blocks
at time. I haven't read the respective source code to confirm my
assumption that small block sizes are used, as my skills are far too
limited, but if that is really the case, wouldn't it make sense to use
bigger writes in order to improve checkpointing performance?

What do you think?


I found a way to speed up checkpointing so it uses the maximum possible
write speed. On the hostnodes we mount the nfs share with the 'sync'
mount option (in order to avoid mutual storage lags between the CTs).
However, when using 'async' the write speed is not dependent on the
block size anymore and is always fast, this means also checkpointing is
fast with 'async'. As we still want the CT's private areas to be mounted
with 'sync', the solution was to use a separate mount for the /vz/dump
directory with mount option 'async'. This way we can achieve maximum
checkpointing speed (which is ~70MB/s on our machines).



Hello, Roman.
It's not correct to compare checkpointing to dd, because it doesn't perform 
sequential writes. We perform a lot of disk seek operations during 
checkpointing.
And yes, NFS works much faster in async mode (async mode shadows seek operations and allows to perform many writes before awaiting for attributes update from 
server), than in sync. This can help you to reduce CPT time.

But you have to fsync resulting checkpointing image on source node to make sure 
that it's consistent on shared storage before resuming on another node.


Roman


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Best regards,
Stanislav Kinsbursky
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[Users] Libvirt slaves Jenkins plugin for openvz?

2013-01-21 Thread Benjamin Henrion 
Hi,

Just wondering if there are users of Jenkins here who are using this plugin:

https://wiki.jenkins-ci.org/display/JENKINS/Libvirt+Slaves+Plugin
http://libvirt.org/drvopenvz.html

It allows to create openvz slaves at build time.

Very handy, but I wonder if someone has experiences with it.

I am giving it a try now, will give you my feedback.

Best,

--
Benjamin Henrion bhenrion at ffii.org
FFII Brussels - +32-484-566109 - +32-2-3500762
In July 2005, after several failed attempts to legalise software
patents in Europe, the patent establishment changed its strategy.
Instead of explicitly seeking to sanction the patentability of
software, they are now seeking to create a central European patent
court, which would establish and enforce patentability rules in their
favor, without any possibility of correction by competing courts or
democratically elected legislators.
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Re: [Users] Libvirt slaves Jenkins plugin for openvz?

2013-01-21 Thread Benjamin Henrion 
On Mon, Jan 21, 2013 at 9:49 PM, Benjamin Henrion b...@udev.org wrote:
 Hi,

 Just wondering if there are users of Jenkins here who are using this plugin:

 https://wiki.jenkins-ci.org/display/JENKINS/Libvirt+Slaves+Plugin
 http://libvirt.org/drvopenvz.html

 It allows to create openvz slaves at build time.

 Very handy, but I wonder if someone has experiences with it.

 I am giving it a try now, will give you my feedback.

Very simple, the GUI only supports XEN/QEMU:

http://wiki.hudson-ci.org/download/attachments/42470710/libvirt-advanced-conf.jpg

-- 
Benjamin Henrion bhenrion at ffii.org
FFII Brussels - +32-484-566109 - +32-2-3500762
In July 2005, after several failed attempts to legalise software
patents in Europe, the patent establishment changed its strategy.
Instead of explicitly seeking to sanction the patentability of
software, they are now seeking to create a central European patent
court, which would establish and enforce patentability rules in their
favor, without any possibility of correction by competing courts or
democratically elected legislators.
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