[Dovecot] Maildir over NFS

[Maxwell Reid]

On Sat, Aug 7, 2010 at 3:06 AM, Stan Hoeppner <stan at hardwarefreak.com>wrote:

> Noel Butler put forth on 8/6/2010 4:29 PM:
>
> > Actually you will not notice any difference. How do you think all the
> > big boys do it now :)  Granted some opted for the SAN approach over NAS,
> > but for mail, NAS is better way to go IMHO and plenty of large services,
> > ISP, corporations, and universities etc, all use NAS.
>
> The protocol overhead of the NFS stack is such that one way latency is in
> the
> 1-50 millisecond range, depending on specific implementations and server
> load.
>

Yes, I would say NFS has greater overhead, but it allows for multi system
access where fiber channel does not unless you're using  clustered
filesystems which have their own issues with latency and lock management....
it's also worth noting  that the latencies between the storage and mail
processing nodes is an insignificant bottle neck compared to the usual
latencies between the client and mail processing nodes.


> Those who would recommend NFS/NAS over fibre channel SAN have no experience
> with fibre channel SANs.



Bold statement there sir :-)   From a price performance ratio, I'd argue NAS
is far superior and scalable, and generally there is far less management
overhead involved with NAS than with SANs, and if you have a commercial high
end NAS, you don't have to deal with the idosyncracies of the host file
system.

In my previous lives running large scale mail systems handling up to 500k
accounts (I work with a team which manages an infrastructure much larger
than that now) The price of latency for a single node using NAS flattens out
as the number of nodes increase.  If you're handling a smaller system with
one or two nodes and don't plan or growing significantly, DAS or SAN should
be fine.



~Max