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 Meyer
ef1c+@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.