In article <[log in to unmask]>, Richard Gambrell
<[log in to unmask]> wrote:
 
> I agree. But we love MPE's reliability and dependablity - if we can
> have it with true OPEN, "plug and play" type standards - then great. If not,
> HP ought to be clearer about it - perhaps calling it HP-SCSI.
> I hope someone from HP can clarify what we "gain" by the "special"
> nature of SCSI disk drives for MPE. Still, I like this situation better
> than a unique, (e.g. HPFL) solution - we do gain from the wider experience
> everyone has with SCSI, even if we do have to buy HP MPE "special" SCSI
drives
> to work with an HP3000.
 
Although not knowing it in detail, I think the big differentiator is
the firmware of these drives' controllers. The mechanical stuff and
phsyical bus specifications are identical, and the mostly identical
design (or use of mass products parts) has lowered the per MB price
for 'MPE discs' as well.
The differences are features like the writing of special on-disc
logs, that can be used for neat stuff like Predictive Support, and
other diagnostics, that help HP not having to tell customers nasty
words like INSTALL too often.
Another very MPE specific criteria is that the disc must support
a mode of writing to disc, where the host has complete control
of the I/O, meaning it is able to wait for the completion of of
a write operation to disc until it REALLY happened every byte in
the sector, and not getting 'fooled' by the on-controller cache.
Otherwise IMAGE logging to disc would be as worthless as the
transaction manager's help to protect your system from data
or file system corruptions.
I also do not know wether the next PC store's SCSI drive provides
a feature like AUTOSPARING, a selfdetection procedure of bad
(or going bad) sectors.
 
I would always go for the reliability.
 
Goetz Neumann,
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