Plesk causing very high server load

[rycrostud]

First our server set up:

Environment
Plesk 7.5.4 (psa v7.5.4_build75060118.18 os_RedHat el3)
Redhat Enterprise Linux 3
MySQL 4.1.18
PHP 4.3.11

Hardware
Dual 1.8Ghz Processors
4GB RAM

Clients/Domains
Clients: 220
Domains: 320

The problem we have is regardless of the time of day or the server load at the time, performing certain functions in Plesk causes server load to go through the roof. Apache, FTP, Mail and MySQL slow down or stop responding altogether. Sometime you get logged out of Plesk too.

There may be other features we know about but certainly going into Setup or adding/deleting clients or domains causes this problem.

For example I went into Setup at 7.30am today when server load was below 0.3. All services just started hanging, the Setup page took about 10 seconds to load and the server load average shot up to over 20.

Any ideas? We have some DB experts looking into it but as yet they have failed to find an answer. They keep suggesting it is just because we have a busy server or some slow queries but I am convinced it is a problem with Plesk itself. This happens every time we go into setup regardless of how busy the server is.

Any suggestions greatly appreciated!

 

[cmaxwell]

Have you checked the iowait on the server as well? RHEL3 has some issues with iowait which causes the loads to be artifically inflated.

- Chris

 

[rycrostud]

Hi,

I'm not sure about iowait. I'll get an engineer to check it out. SW Soft have recommended upgrading the kernel.

 

[cmaxwell]

Upgrading the kernel is probably to resolve the iowait issue - if you run "top" on the command line you will see the iowait value as well as the loads.

On a RHEL3 server any iowait will boost the loads quite substantially.

It may not be iowait that's affecting your box, however, but I am speaking from our own experience with a similar situation.

- Chris

 

[rycrostud]

Well they haven't updated the kernal yet. However they think they have ruled out a problem with iowait.

Doing my own investigations I have found that restarting MySQL temporarily fixes the problem, but over time Plesk gets gradually slower and slower when performing these functions. Another MySQL restart and everything is nice and zippy for a while.

I am assuming this is probably something to do with our MySQL query caching settings, the slow query log or something like that.

Any more ideas (thatnks for your suggestions so far by the way. Very helpful indeed).

 

[cmaxwell]

I recommend you download mytop and install it - it lets you monitor MySQL connections on the server:

http://jeremy.zawodny.com/mysql/mytop/

You can run it with this command:

mytop -uadmin -p`cat /etc/psa/.psa.shadow`

Hopefully that will show up the MySQL bottleneck.

- Chris

 

[rycrostud]

Well this just gets more bizzare.

I installed mytop but it didn't turn out to be much use. The problem is that while Plesk is causing these load issues the SSH terminal just hangs. When Plesk has finished you are spat out of mytop before it has a chance to refresh so it is impossible to see which queries are running.

From using top -c I think I have narrowed this down to a problem with domain.sh/domain.php but I will need to do some command line tests to confirm. Unfortunately those files are encoded so I can't see what queries are being performed.

Any suggestions greatly appreciated.

 

[cmaxwell]

Recommend you submit a bug report on this to SWsoft by emailing [email protected]

- Chris