[Dovecot] index IO patterns

[Stan Hoeppner]

On 5/11/2012 1:41 AM, Cor Bosman wrote:
> Hey all, we're in the process of checking out alternatives to our index storage.  We're currently storing indexes on a NetApp Metrocluster which works fine, but is very expensive. We're planning a few different setups and doing some actual performance tests on them.  

Hi Cor,

> Does anyone know some of the IO patterns of the indexes? For instance:
> 
> - mostly random reads or linear reads/writes? 
> - average size of reads and writes?
> - how many read/writes on average for a specific mailbox size?
> 
> Anyone do any measurements of this kind?

Mail is always a random IO workload, unless your mailbox count is 1,
whether accessing indexes or mail files.  Regarding the other two
questions, you'll likely need to take your own measurements.

> Alternatively, does anyone have any experience with other redundant storage options? Im thinking things like MooseFS, DRBD, etc? 

You seem to be interested in multi-site clustering/failover solutions,
not simply redundant storage.  These two are clustering software
solutions but DRBD is not suitable for multi-site use, and MooseFS
doesn't seem to be either.  MooseFS is based heavily on FUSE, so
performance will be far less than optimal.  MooseFS is a distributed
filesystem, and as with all other distributed/cluster filesystems its
metadata performance will suffer, eliminating maildir as a mail store
option.

Can you provide more specifics on your actual storage architecture needs?

-- 
Stan