Hard Disk questions

[John B. Milton]

In article <701 at argon.UUCP> ebh at argon.UUCP (Ed Horch) writes:
>In article <19995 at cup.portal.com> thad at cup.portal.com (Thad P Floryan) writes:
>>MB, formatted (std, 17 sec/trk)	42.8			71.2
>>
>>MB, formatted (UNIXPC, 16 sec/trk)	40.3			67.1
>>(ignoring the spare sec per track)
>
>What does the Unix PC do with that extra sector?  Is that how it
>remaps bad blocks?

Yes, that's how "it" does it. 1/17th of the total formatted disk capacity is
thrown away to make bad block mapping easier. If there is more than one bad
sector on a track, it uses the 17th sector from another track. Below is the
output from "iv -vt /dev/rfp000", which shows all the formatting info from the
VHB (Volume Home Block), as well as a dump of the bad block table, which I
sorted after including in this article, careful examination will show that this
bad block table was not created entirely on the first pass.

One could argue that a better bad block scheme should have been developed, but
this one simplified other problems (1k "driver" logical blocks), and runs
fairly quickly.

Winchester disk
Volume Name: WINCHE
917 Cylinders. 9 Heads per Cylinder.
There are 17 Physical Sectors (of 512 bytes) per Track.
	153 Physical Sectors per Cylinder, 140301 Physical Sectors per Disk.
There are 8 Logical Blocks (of 1024 bytes) per Track.
	72 Logical Blocks per Cylinder, 66024 Logical Blocks per Disk.
The Step Rate supplied to the Controller is 0.
Partition 0: start Track=0, size (in Blocks)=72
Partition 1: start Track=9, size (in Blocks)=5000
Partition 2: start Track=634, size (in Blocks)=60952
Loader starts at Block 2 (size=23 Blocks).
Bad Block Table starts at Block 1 (size=1 Blocks).
Cylinder  175, Track  3, Sector  4, uses Track  3, Sector 16 as Alternate.
Cylinder  352, Track  2, Sector  0, uses Track  3, Sector 16 as Alternate.
Cylinder  352, Track  2, Sector  1, uses Track  1, Sector 16 as Alternate.
Cylinder  352, Track  2, Sector 12, uses Track  2, Sector 16 as Alternate.
Cylinder  359, Track  4, Sector  0, uses Track  3, Sector 16 as Alternate.
Cylinder  359, Track  4, Sector  1, uses Track  6, Sector 16 as Alternate.
Cylinder  359, Track  4, Sector 12, uses Track  4, Sector 16 as Alternate.
Cylinder  359, Track  4, Sector 13, uses Track  5, Sector 16 as Alternate.
Cylinder  449, Track  6, Sector 12, uses Track  6, Sector 16 as Alternate.
Cylinder  510, Track  7, Sector  0, uses Track  8, Sector 16 as Alternate.
Cylinder  510, Track  7, Sector  1, uses Track  7, Sector 16 as Alternate.
Cylinder  643, Track  6, Sector  1, uses Track  6, Sector 16 as Alternate.
Cylinder  763, Track  6, Sector  0, uses Track  6, Sector 16 as Alternate.
Cylinder  763, Track  6, Sector  1, uses Track  7, Sector 16 as Alternate.
Cylinder  855, Track  8, Sector  0, uses Track  8, Sector 16 as Alternate.
Cylinder  855, Track  8, Sector  1, uses Track  0, Sector 16 as Alternate.
The Bad Block Table contains 16 entries.

John
-- 
John Bly Milton IV, jbm at uncle.UUCP, n8emr!uncle!jbm at osu-cis.cis.ohio-state.edu
(614) h:294-4823, w:466-9324; N8KSN, AMPR: 44.70.0.52; Don't FLAME, inform!