Re: Large spool mboxes => slow?

On Thu, 9 Mar 2006, Alan Brown wrote:

> On Thu, 9 Mar 2006, Hugh Sasse wrote:
> 
> > > Also enable server mode.  enable caching of temp dir
> >
> > Enabling server mode is not possible given some types of client (from
> > my reading of the docs).  I don't know all the clients people use, so
> > I must err on the side of caution.  Or is that paranoid in 2006?
> 
> Server mode is only risky under the following circumstrances:
> 
> 1: Access is made via POP3 and local disk (or a non-compatible imap3 server)
>    which use non-compatible locking methods.
> 
> 2: Clients _simultaneously_ access using both methods.
> 
> I used server mode for many years in a mixed environment with no
> problemss - by ensuring the lock mechanisms used were compatible.
> 
> Even without that, it is highly unusual for users to use both pop3 and
> local disk access methods - those that do are usually technically savvy
> enough to understand the corruption risk and not use both methods
> simultaneously once it is explained to them.

OK, then I will certainly enable it for the large users. It's just
that usage patterns are a "known unknown", and I'm reluctant to get
caught by the "unknown unknowns" :-)
> 
> > Thanks.  I'm not au fait with disk internals, and thought that some
> > disks may have many heads
> 
> They do (one per platter), but....
> 
> >, not just to read one cylinder at a time,
> 
> Only one head is ever active at one time with current commonly available
> commercial available disk techmology.
> 
> The only way to achieve what you want is to use a suitable hardware
> controller capable of simultaneously addressing multiple drive busses
> (despite the other advantages of scsi, only one drive can be addressed
> at a time on any given physical scsi bus.

OK, I thought there might have been developments I'd not kept up with.
Thanks.
> 
> Large scale (S)ATA or SASI raid controllers give better results most of
> the time in terms of overall bandwidth. Latencies cannot be redcued
> below seek+rotation times even with fancy controllers.
> 
> For ultimate bandwidth andlatencies, suitable solid state arrays are the
> only way to go - but are extremely expensive.

To be nonvolatile and fast they would be.  I'm trying to get another
disk for this system, but I doubt they'd stretch to RAID.  Thank you 
anyway, it's useful stuff to keep in mind.
> 
        Hugh