Subject: RE: partitioning RD54
To: None <>
From: None <>
List: port-vax
Date: 02/27/2000 08:37:22
>Is there any particular reason why the disktab entry specifies 1225 cylinders,
>rather than the manufacturer-specified 1224?

Because the folks who constructed the disktab entry didn't know what
what they were doing.

>  The end of partition f looks
>like it would be at sector 311628, somewhat lower than the 312120 sectors
>the drive should have or the 312375 sectors given in the geometry section.
>How many sectors does the RQDX3 actually make available on an RD54?

Gack!!!  I ranted and raved about this here 3 or 4 years ago, and they *still*
haven't fixed this brain-damaged disktab entry?  Well, time to rant and
rave again:

A RD54 on a RQDX3 has 311300 "normal" blocks.  Those "other" sectors are
reserved for the RCT and for replacement blocks.  The numbers calculated
from the drive's physical geometry are meaningless.  They have been
meaningless since the first UDA50 rolled off the assembly line almost
a quarter-century ago, giving us freedom from having to know the physical
geometry of a drive.  

Well, that rant and rave probably had as much effect (ZERO) as the last
time I did it, but don't say I didn't warn you.  In particular, on many
MSCP disk controllers if you issue writes past the end of the "user
area" of the disk you'll clobber the RCT.  If you do that, well, you're
almost totally screwed.  If you've got XXDP+ on a PDP-11 you can use
ZRQC?? to go in and salvage the RCT in some circumstances, but on a
MicroVAX you're screwed because the field service diagnostics can't
salvage the RCT.  Heck, the field-service diagnostics are barely capable
of formatting an already good RD54 into a RD54.

As to why you get a write error trying to newfs your RD54, I don't think
the brain-damaged partition table is the reason here, as you almost certainly
aren't running up against the end of the disk.