[PLUG] Tape Drives and Power Supplies ( was strange crashes ... )

[Keith Lofstrom]

> "Keith" == Keith Lofstrom <keithl at kl-ic.com> writes:
> 
> Keith> Unless a tape drive is designed specifically with power supply
> Keith> friendliness in mind, it is probably the nastiest power load in
> Keith> your box.  [...]

On Thu, Jan 06, 2005 at 10:25:10AM -0800, Russell Senior wrote:
> The only problem with this scenario I see is that the tape drive is an
> external unit and it is being powered independently from the computer,
> ...

Huh.  Well, one theory all shot to hell ... ;-)

Check the note I just sent out about UPS battery failures.  While a
voltage sag in the tape box can lock up the SCSI bus (I have seen that
happen), I've never seen it take out the whole OS.  Unless your disks
are on the same SCSI bus, too, in which case all sorts of nonsense
can result.

Associated story of tapes in external boxes:  I have a largish heap
of old DC300/DC600 cartridge tapes, with lots of tiny little backup 
images on them.  To copy them onto disk, I built "tapezilla", an
external box with 4 half-height drives in it.  The power supply in
the box was designed for one tape and one disk.  I found I could only
reliably read two tape drives at once - three or more would sag the
supply and hang the SCSI bus.  The connected Linux box stayed up 
just fine after the SCSI hang, though it needed to be power-cycled
to clear the hang.

Keith

-- 
Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
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