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
