[Koha] Mystery system slowdown

[Agnes Rivers-Moore]

Dear friends

We have six libraries running Koha 3.00.06.
The system runs Redhat, with 6 virtual Xen servers.

Problem #1
 From time to time, at various times of day one or more of the Koha 
systems will slow down and stop.

We can watch the CPU graph on the virtual machine  manager - it usually 
drops to less than 1% use for a few minutes.
At this point we have librarians staring at unresponsive Koha screens - 
connecting... connecting...
The virtual server desktop is unresponsive even at the physical server.
We cannot connect with a VNC client or browse in.
This is very frustrating when the CPU graph implies that the server is 
apparently not busy.

Then the CPU use will ramp rapidly up to 12.4% use (which is pretty much 
full capacity on our virtual server setup).
It stays there - and although it may have recovered once or twice from 
this, usually we have to kill the server.

Sometimes we force the VM to shut down, and then restart it, and can see 
zebra searches happening with Top. However we may still be unable to log 
in with VNC or connect from local client browsers.

This is really difficult to track down because we have not found 
associated error messages, and by the time we get to them, the servers 
seem to be showing low load, but we may be missing some initiating event.

That is problem #1

Here is problem #2
We have also noticed that opac-search.pl and mysqld is causing heavy 
loading.
Within the virtual server we have multiple cpus and the load is shared 
between them,
However, often opac-search.pl is around 30%, and mysqld alone is using 
close to half of the virtual server's CPU capacity.
The records we have in this single site library do not have large 
numbers of items attached to any one biblio record.
There was a discussion in March about something like this a year ago, 
but I can't see a resolution.

Does anyone have any ideas on either of these issues?
Hoping  someone from the developer group might have some ideas.

Agnes


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Hanover Public Library.
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