From: forsyth@plan9.cs.york.ac.uk forsyth@plan9.cs.york.ac.uk
Subject: Standalone SPARC.
Date: Tue, 3 Oct 1995 20:08:47 -0400 [thread overview]
Message-ID: <19951004000847.qlz2MUhQCZzKh9Kk_CPwCW0l9GRru466qwzI_hj2m50@z> (raw)
>>look like SunOS and plan9 are counting blocks the same way. Anyone know
>>how to reconcile the numbers?
i think you'll find that SunOS cheats in two ways:
- it reserves a few cylinders (`alt cyl') to provide replacement blocks
for bad blocks
- more seriously (in terms of the amount of space), SunOS has the notion
of (say) a 500 Mbyte disc. that might be implemented by a disc that
is 535 mbytes or 520 mbytes or precisely 500 mbytes (formatted).
it simplifies supplying and replacing discs, when the discs come
from several manufacturers, with slightly different capacities.
Plan 9 displays the results of a SCSI `get capacity' request, which
should be precise.
see /etc/format.dat on SunOS for more details.
it isn't a bad idea, given the practical restrictions, but it does lead
to the situation you describe.
oh yes. the `bad block replacement' area is probably not needed on
a modern system; a good SCSI drive should implement the `block replace'
function.
next reply other threads:[~1995-10-04 0:08 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
1995-10-04 0:08 forsyth [this message]
-- strict thread matches above, loose matches on Subject: below --
1995-10-11 7:23 Al
1995-10-10 13:21 Steve
1995-10-10 10:23 Andrew
1995-10-07 17:34 Byron
1995-10-07 9:01 Alex
1995-10-07 1:13 forsyth
1995-10-07 0:30 Jim
1995-10-03 23:12 Jim
1995-10-03 17:32 Byron
1995-10-03 14:14 Reg
1995-10-03 5:09 Alex
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