[Dovecot] IO rate quotas?

Alan Brown ajb2 at mssl.ucl.ac.uk
Mon Apr 11 13:58:58 EEST 2011

From: Timo Sirainen <tss at iki.fi>
Subject: Re: [Dovecot] IO rate quotas?

> So a single process that is reading files fast enough from disk can
> cause disk IO to spike in a way that makes all other processes wait for
> available disk IO?

It's not a single process.

Thunderbird's newest defaults are to syncronize every folder and it will 
open one connectrion per folder in order to do that.

Appropriate disk/swappiness/readahead/cache tuning is required - along 
with enough ram to cope with several users trying this at once.

The underlaying filesystem is also important. as a for-instance, this 
kind of load with maildir format will effectively _kill_ a GFS box.

Our fix was to install systemwide defaults on managed systems to not 
synchronize (not needed, the home directories are on network storage 
anyway) and to ask people to check/unset this on laptops/etc

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