PD-2 LF-D100
The information below might be useful to very few people, but nevertheless if it can help others I would be glad.
In the mid 90's, I used Phase Change Rewritable optical disks ('PD').
These where 650MB of rewritable optical disks. My TORAY writer died
around 2000. By then the PD technology became the basis for the DVD-RAM
standard. In order to be able to use by previous PD optical disks. I
purchased a Panasonic LF-D100 unit. This unit is capable of reading
legacy 650MB PD Optical disks as well as the initial 2.6/5.2 GB DVD-RAM
disks. Unfortunately it cannot read (or write) to the newer 9.4GB
DVD-RAM disks.
This unit worked well for me for many years up-to the Linux 2.2 kernel,
but sometime around 2.4 I lost the capability to read the disks. By
then, I had stopped using optical disks on a regular basis having
switched to writable CD-ROM's so I did not pursue the matter. Reecently
I wanted to access some of my older PD and DVD-RAM backups I had
created in the past.
Luckily, using the latest 2.6 kernels can read these disks again.
Originally, in the Linux 2.2 days, I used the optical disks as
basically slow hard-drives. That meant that the disks where
partitionned as hard-disks, with a single ext2 partition (with the
noatime setting). It seems, that around the 2.4 kernel, the ability to
simply read optical media format was lost. It appears the support for
partitioning was lost by default, and the kernel assumed that optical
disk would be using the UDF filesystem. a filesystem more adapted to optical media.
That said, while the disks cannot be read as is by simply inserting the
media in the unit, with a few workarounds, the disks can easily be read
and written to. Basically the trick, is simply to bypass the first
track of the optical disk that was lost in the optical disk partioning
process using the loopback device.
Here is what I use: (note the different media require different offsets for the loopback device)
PD Disks (650MB)
To mount:
[root@localhost log]# sfdisk -l -uS /dev/scd0
Disk /dev/scd0: cannot get geometry
Disk /dev/scd0: 0 cylinders, 0 heads, 0 sectors/track
Warning: The partition table looks like it was made
for C/H/S=*/64/32 (instead of 0/0/0).
For this listing I'll assume that geometry.
Units = sectors of 512 bytes, counting from 0
Device Boot Start End #sectors Id System
/dev/scd0p1 32 1298431 1298400 83 Linux
/dev/scd0p2 0 - 0 0 Empty
/dev/scd0p3 0 - 0 0 Empty
/dev/scd0p4 0 - 0 0 Empty
[root@localhost log]# losetup -o 16384 /dev/loop0 /dev/scd0
[root@localhost log]# mount -t ext2 -o ro /dev/loop0 /media/dvdrom/
[root@localhost log]# df
Filesystem 1K-blocks Used Available Use% Mounted on
....
/dev/loop0 628399 317502 278437 54% /media/dvdrom
To unmount:
[root@localhost log]# umount /media/dvdrom
[root@localhost log]# losetup -d /dev/loop0
2.6 GB DVD-RAM (Side A or B)
[root@localhost log]# sfdisk -l -uS /dev/scd0
Disk /dev/scd0: cannot get geometry
Disk /dev/scd0: 0 cylinders, 0 heads, 0 sectors/track
Warning: The partition table looks like it was made
for C/H/S=*/64/32 (instead of 0/0/0).
For this listing I'll assume that geometry.
Units = sectors of 512 bytes, counting from 0
Device Boot Start End #sectors Id System
/dev/scd0p1 32 4874239 4874208 83 Linux
/dev/scd0p2 0 - 0 0 Empty
/dev/scd0p3 0 - 0 0 Empty
/dev/scd0p4 0 - 0 0 Empty
[root@localhost log]# losetup -o 65536 /dev/loop0 /dev/scd0
[root@localhost log]# mount -t ext2 -o ro /dev/loop0 /media/dvdrom/
[root@localhost log]# df
Filesystem 1K-blocks Used Available Use% Mounted on
.....
/dev/loop0 2398752 1991340 285560 88% /media/dvdrom
To unmount:
[root@localhost log]# umount /media/dvdrom
[root@localhost log]# losetup -d /dev/loop0