jcm@amara.UUCP (John Martin) (12/21/90)
The "/etc/disktab" entry for my DECstation 3100 running Ultrix 4.0 with
an RZ55 looks like this:
------
rz55|RZ55|DEC RZ55 Winchester:\
:ty=winchester:ns#36:nt#15:nc#1224:\
^^ ^^ ^^^^
:pa#32768:ba#8192:fa#1024:\
:pb#131072:bb#8192:fb#1024:\
:pc#649040:bc#8192:fc#1024:\
^^^^^^
:pd#152446:bd#8192:fd#1024:\
:pe#152446:be#8192:fe#1024:\
:pf#180308:bf#8192:ff#1024:\
:pg#485200:bg#8192:fg#1024:\
:ph#0:bh#8192:fh#1024:
------
Looking at the highlighted numbers here, though, something just doesn't
seem to work out. The value for "pc", by convention, should be the
number of available sectors on the disk, but a naive calculation of
sectors*tracks*cylinders would yield 36*15*1224=660960 sectors, not
649040 sectors as indicated by the "pc" entry.
There seem to be several disks listed in "/etc/disktab" that have similar
sorts of discrepancies:
------
rd31|RD31|DEC RD31 Winchester: ns=17, nt= 4, nc= 615, pc= 41560, calc= 41820
rd32|RD32|DEC RD32 Winchester: ns=17, nt= 6, nc= 820, pc= 83236, calc= 83640
rd33|RD33|DEC RD33 Winchester: ns=17, nt= 7, nc=1170, pc= 138565, calc= 139230
rd53|RD53|DEC RD53 Winchester: ns=17, nt= 8, nc=1024, pc= 138672, calc= 139264
ra80|RA80|DEC RA80 Winchester: ns=31, nt=14, nc= 546, pc= 237212, calc= 236964
rd54|RD54|DEC RD54 Winchester: ns=17, nt=15, nc=1221, pc= 311200, calc= 311355
rz55|RZ55|DEC RZ55 Winchester: ns=36, nt=15, nc=1224, pc= 649040, calc= 660960
rz56|RZ56|DEC RZ56 Winchester: ns=54, nt=15, nc=1632, pc=1299174, calc=1321920
rz57|RZ57|DEC RZ57 Winchester: ns=71, nt=15, nc=1925, pc=2025788, calc=2050125
ra92|RA92|DEC RA92 Winchester: ns=69, nt=13, nc=3279, pc=2940951, calc=2941263
------
What am I missing?
* Where does the magic 649040 value come from?
* Is the "pc" entry wrong? Are the "ns", "nt" and "nc" values wrong?
* Perhaps the remaining 11920 sectors on the RZ55 are preallocated to
hold bad sector remappings?
* If so, how/when do they get preallocated?
* How's the 11920 calculated?
* Which entries in TFM describe the process, or what other sources
talk about it?
* Is this really worth worrying about?
Please email any ideas you have, I'll summarize in about two weeks.
Regards,
--
John Martin, Applied Dynamics International, Ann Arbor, MI, (313)973-1300
jcm@adi.com || jcm%amara.uucp@mailgw.cc.umich.edu || ...uunet!sharkey!amara!jcm
"How many times over the past six months did you, or people working for you,
write some program fragment for table searching?" -- Bertrand Meyeref1c+@andrew.cmu.edu (Esther Filderman) (12/22/90)
This reminds me of the possible problem that I am seeing on our rz57s
which live on a Decstation 5000/200. The disktab entry says that the size
of pc should be 2025788, but chpt -q says something totally different. [I
don't have the exact number here, but it's something like 195xxxx.] When
I called for software support I was first told that it was the way that
the operating system was installed [ultrix 3.1d had been copied from a
Decstation 3100] and that this confused the machine, and that I should
reload software. So instead we installed Ultrix 4.1 from tk50 and
voila, chpt and the disktab still don't match.
Am I incorrect in thinking that they should? They do for every other drive
on every other system I have, including Vaxstation 3100 with rz23, Decstation
3100 with rz24, vax 3200 with ra82, vax 6410 with ra90, from Ultrix 3.0 [vax]
to Ultrix 4.1 [vax and risc]. Could there be incorrect disktabs out there?
Has anyone else seen similar things with rz57s?
Thanks,
Esther
-----------------
Esther C. Filderman ef1c+@andrew.cmu.edu
System Manager Computing Services
Mercury Project Carnegie Mellon University
They are gardeners and carpenters.
They are not tomato men.