Wren VI format.dat query

[Geoffrey H. Cooper]

In article <4967 at brazos.Rice.edu> dma at gandalf.berkeley.edu (D. Mark Abrahams) writes:
>X-Sun-Spots-Digest: Volume 9, Issue 39, message 12
>
>I'm particularly interested in the Wren VI (on the SS1, if it matters) as
>this is the disk I plan to purchase.  (The vendor choice was made on
>overall price including hardware maintenance price, not claimed Mb).  Here
>is the format.dat entry this vendor uses.
>
>disk_type = "CDC WrenVI 94196-766" \
>	: ctlr = MD21 : fmt_time = 3 \
>	: trks_zone = 15 : asect = 6 \
>	: ncyl = 1626 : acyl = 2 : pcyl = 1632 : nhead = 15 : nsect = 53 \
>	: rpm = 3600 : bpt = 30170
>
>This gives ncyl*head*nsect = 1626*15*53 = 1292670 sectors = "only" 646Mb.
>Can this be improved?  If you are using a Wren VI, what is your format.dat
>entry and how did you arrive at it?

I had a lot of trouble figuring out what to use for our Wren VI's on
SS1's.  After a few calls around (note: Seagate has a nice 900 number for
answering questions on this, I came up with the following:

sd3: <CDC Wren VI 94191-766 (1632x52x512) cyl 1630 alt 2 hd 15 sec 52>

i.e., 512 bytes/cyl, 1632 cyl total, 2 spare cyl's, 52 sectors/track.  (15
heads, but that isn't negotiable).   My experience was the 53 sectors
didn't work (maybe I should try the above), and that 54 died immediately.
This despite Seagates quoting of 54 512-byte sectors per track.  I have
presumed that sun format steals 2 sectors per track for the bad block
list, but don't know this to be correct.

I believe that disk utilization would be somewhat higher with 1024 byte
sectors, since less room is allocated to inter-sector gaps and labelling.
I was surprised to find that this doesn't appear to be supported anywhere
(and wasted a morning improperly formatting my disk).

Actually, the REAL trick would be to figure out what format.dat
corresponds to the formatting that CDC already puts on the drive, or
create some program to make that work right.  To get Sun to accept the bad
sector list, I had to re-format (2+ hours).  This is a pain when the disk
comes formatted from CDC, and really only needs a label and an analysis
pass.

That is my experience.  I'll be eager to find out if there is another
technique that works better.

BTW, is the format of the /etc/format.dat hiding in the SysAdmin manual
somewhere?  I can't find a man page that describes it.

Now: how long before I have to buy a Wren VII to be able to keep all this
PD stuff on line at once...

geof at aurora.com / aurora!geof at decwrl.dec.com / geof%aurora.com at decwrl.dec.com