C Partition

[COTTRELL, JAMES]

/*
> >About that c partition... c accesses the whole disk including 
> >the space reserved bad blocks. 
> ---
> Wizards:  Is this really true?

Yes.

> Am I playing with fire by having a c partition
> on a CDC 9766 (like an RM05) controlled by an SI 9400 controller?

Yes and No. As long as you never back up disk packs by making identical
copies via `dd' you will be okay. If your disks are perfect (no bad
blox) you can even do that. Don't let the disk get too full tho, or that
last track might get allocated as data. Hopefully, they should be the
last blox allocated. When you make your file system partition C, give it
less blox. Sutract off that last track. Change the `pc' parameter in
/etc/disktab from 500384 to 499776. I see no reason to include the last
track in the C partition description. SUN 2.0 doesn't. 

Try to keep straight what's going on here tho. The hp driver has the
limits of the partitions wired into it. Partitions start where
/etc/disktab says they do and are only as big as it says. If you want to
make them smaller fine. The driver never looks at /etc/disktab tho.
Newfs does. You can always make an almost duplicate entry, say ZDZ9766
and then do `newfs hp#c ZDZ9766'. The super block says the disk is
short, but you can get at the last track thru the raw device. 

> I'm interested in the c partition part, ...
> not in flames about the 9766 or SI.

How about a testimony then? We have an SI 9900 (not 9400) controlling
an eagle and a 9766. SI gave us a tape with a new hp.c along with
a bunch of utilities. How does *online* formatting sound to you!?!
And bad block redirexion with the bad data automatically forwarded!
And it even works on our DEC RM03's & our other SI 9400 controlling
two 9762 (RM03's). Only (cosmetic) complaint is that everytime the
system boots (or mounts the A partition) the bad block list
prints on the console. Should be easy to remove tho, or redirect
somewhere else.

> I'm running under VAX 4.1 BSD UNIX.

I'm running 4.2 & have never seen 4.1, so I might be off the wall.

> Jon Eichelberger
> eichelbe at NADC

	jim		cottrell at nbs
*/
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