[Dovecot] Effects of migration

[Andy Dills]

On Thu, 6 Mar 2008, Timo Sirainen wrote:

> On Wed, 2008-03-05 at 11:23 -0500, Andy Dills wrote:
> 
> > The impact has been severe! Even with NFS-stored indexes, our netapp is 
> > seeing 1/6th of the NFS ops per second, and its CPU utilization is now at 
> > 1/3rd previous levels.
> 
> Have you thought about enabling Squat indexes? I'd like to know how much
> it would affect I/O and CPU usage in larger installations. CPU grows
> (maybe a lot) but searches should be faster and use very little I/O as a
> result.

By CPU, do you mean local server (nfs client) CPU or netapp CPU (nfs 
server)?

I'm guessing the former...for what it's worth, for those who have yet to 
have the pleasure of using a Netapp, the CPU utilization is basically your 
ultimate barometer of utilization with netapps. As long as you don't start 
hitting 90% CPU consistently, they will provide better throughput than 
local SCSI disks. The CPU tops out well before the I/O, a nice change of 
pace. 

Local CPU is of little concern typically, as mail serving (filtering is 
handled elsewhere) is almost purely I/O.

However, I'm not sure how much value I would place on optimizing searches 
at this point...do users really do much of that? It seems to be 
potentially valuable yet underutilized.

Do you have some links so I can educate myself more about squat indexes?

Andy

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Andy Dills
Xecunet, Inc.
www.xecu.net
301-682-9972
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