-tao vs -sao

[Peter Rabbitson <rabbit@rabbit.us>]

Hello

I am confused by the way cdrecord handles burning of isos while in the
default -tao mode. The source iso is 719603712 bytes long which divided by
2048 yields 351369 sectors.

After ./cdrecord -sao ./KNOPPIX_V3.8.1-2005-04-08-EN.iso I get:

~# ./cdrecord -toc
Cdrecord-Clone 2.01 (i586-pc-linux-gnu) ....
....
first: 1 last 1
track:   1 lba:         0 (        0) 00:02:00 adr: 1 control: 4 mode: 1
track:lout lba:    351369 (  1405476) 78:06:69 adr: 1 control: 4 mode: -1


However after ./cdrecord -tao ./KNOPPIX_V3.8.1-2005-04-08-EN.iso I get:

~# ./cdrecord -toc
Cdrecord-Clone 2.01 (i586-pc-linux-gnu) ....
....
first: 1 last 1
track:   1 lba:         0 (        0) 00:02:00 adr: 1 control: 4 mode: 1
track:lout lba:    351371 (  1405484) 78:06:71 adr: 1 control: 4 mode: -1

Furthermore if I try to read those extra sectors (and the last two of the 
original image) I get this:

~# dd if=/dev/hdd of=some.image bs=2k skip=351367 count=4
dd: reading `/dev/hdd': Input/output error
1+0 records in
1+0 records out
2048 bytes transferred in 14.034006 seconds (146 bytes/sec)

Not only the two extra sectors can not be read, but the last sector of the 
initial 351369 is not accessible either.

The same thing happens with any iso image on 3 different burners, two
versions of cdrecord (2.01 and the one that comes with debian/sid), both
with kernels 2.6 and 2.4. I could just keep writing my isos in DAO mode and
be happy, but I just don't see why the default TAO (and it is chosen to be
default for some reason) does not work as needed.

Any suggestions and/or reading references are highly appreciated

Thank you

Peter