[rescue] G4 pricing

[Peter Corlett]

On 17 Aug 2006, at 22:08, Mike Meredith wrote:
> On Thu, 17 Aug 2006 19:48:05 +0100, Peter Corlett wrote:
>> In any case, disk is cheap and you might as well have loads of swap
>> on a Linux box and use it to back tmpfs on /tmp, /var/spool/exim4/
>> cache and so on.
>
> Ouch! Most of /var/spool/exim certainly doesn't belong on a tmpfs
> filesystem ... an MTA is supposed to ensure that a message is securely
> written to non-volatile storage before returning the final 'OK' in an
> SMTP session. It's fine to have /var/spool/exim/db on tmpfs though ...
> which is the hottest point of that hot directory.

Mail.app broke that line inappropriately, and I got the name of the  
directory slightly wrong. The spool is, indeed, on a regular ext3  
filesystem, albeit inside a Xen domU where I suspect the fsync()s  
don't cause an *immediate* flush to disk but only when the dom0 gets  
round to it up to 30s later.

> Of course I'm somewhat prejudiced in this matter being an old- 
> fashioned
> mail administrator ... in reality modern systems are reliable enough
> that you may choose to put /var/spool/exim on tmpfs and cope with the
> risk of lost messages.

Ah, no, I wouldn't personally do that. I *would* consider using a  
solid-state disk for spool, but they're not at all the same thing,  
and expensive enough that building another mailserver may be more  
productive.

I think we're both actually singing from the same songsheet here.