Re: Locking and concurrency -- system considerations

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Author: Piete Brooks
Date:  
To: Jon Morby
CC: exim-users
Subject: Re: Locking and concurrency -- system considerations
> In the environment I envisage running Exim shared spools are essential.

Hmm -- interesting to see how others think !

NFS is fine for user filespaces, but it seems odd to me to have NFS mounted
(I assume that's how you are sharing) spool dirs ...

> we have several machines (relay-1 -> relay-15 currently) all of which share
> one of two spools.


On two fileservers ?
What if one of the FS dies ? you loose 8 relays ??

> Being restricted to one spool per delivery client would be a restriction I
> wouldn't like to have to live with.


Interesting ...

> (What happens when one of your relays goes down, and you've got a couple of
> thousand messages in it's queue?)


You move the disks to a spare CPU, and off you go !

What happens to you if one of your two file servers die ??

> The mail gets delayed until you can bring another box up and mount that spool.


Yup -- what about your fileservers ?

> Unacceptable in todays market with consumers rather than techies coming onto
> the Net.


It depends what kind of support you have ...
Assuming you have "outside hours" cover, someone just replugs the disks,
and email is delayed for 5 mins or so.
Is that *really* unaccepatble ?
What is the MTBF for your servers ?


I'm not trying to knock the way you do things (I do things in *really* weird
ways !), just trying to see if your configuration is really optimal for you,
or whether some re-arrangement might improve your througput and resilience.
[ e.g. are you raaid boxes dual ported ? Do you need to replug, or can you
just do a mount when the "other" server is noticed to be down ?
]

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