[rt-users] Severe performance problems suddenly in RT 3.8.2

[Tim Cutts]

On 17 Feb 2009, at 6:39 pm, Ruslan Zakirov wrote:

> I hope you see that mysql examined only 27 rows and spend 240 seconds
> to do that. I suspect that it's related to very high IO activity that
> were going parallel with this query and blocked mysql's IO requests.

That was my worry.  I've shuffled the virtual machine onto a physical  
server with no other VM's running, and the performance problem remains  
the same.  The graph of disk I/O from the VMware control center shows  
the system doing no I/O at all until I start the SELECT, and then it  
goes to about 15 MB/sec for the duration of the query.

So if there is contention, it's not at the level of the physical  
server's I/O.  However, it could still be contention for the SAN  
volume which hosts the virtual machine; I find this hard to believe  
since the total I/O of all three physical servers is pretty low, but I  
will try tomorrow to see what happens if I move the virtual machine to  
its own piece of storage,

Tim


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