Francisco Jose Montilla <[EMAIL PROTECTED]> wrote:
> - Doesn't SCSI controllers use parity? (Although you have to
> enable it, of course)
Yes. However some of them do not use ``parity'' on the PCI bus, or in
their internal memory. This has happened to me (at a very stressing
case, with a bad mother board, two SCSI cards, very high burst
transfer rates: changing mother board fixed the problem. The
mother board was fine for single-card application).
There, as you said, RAID will be of no help. Backups may. RAID
will also be no help if the operating system goes mad. If the OS
writes garbage, all the mirrors will get perfectly reconstructible
and fault-tolerant garbage.
> if a cable or terminator on one channel were to go bad, the system would
> continue to function.
right.
> When hot-swapping a harddrive, the RAID card must temporarily stop the
> SCSI channel the drive is attached to. If the other drive in a RAID one
This is the theory
> I agree completely with the first statement. But the second sounds
> somewhat odd to me. I can hotadd or hotremove a disk on linux with sw RAID
no, sorry, you can't. You can by software (scsi-add/remove-single-device).
If you do not have PROPER electrical cabling which ensures disk insertion
and removal do not perturbate the SCSI bus in any way, you need separate
channels.
You can buy special enclosures which have those capabilities. It's
not software (well, one could design a Linux ``suspend SCSI'' fonctionnality
for the 5 seconds of insertion in software).
