Multisession DVD

[Flash]

...I didn't even know there are mini-dvds!

They are the same size as mini-CDs (8 cm) and hold 1.4 GB. Memorex have an 8cm mini DVD-RW with "DuraLayer" scratch-resistant coating. I bought a 3-pack for $15 to try out. They boot fine in my computer.

DVDs are better than CDs in another way: the data layer is sandwiched in the center of the thickness of the disk, not on the back side close to the surface where a scratch can easily obliterate it.

[Ted Dog]

The improvements with xgine and the playback of larger video files quickly in 1.05Beta looking good. I am looking to work on the new alpha when it is released.. - Ted Dog

[BarryK]

Ted,
Note, although 1.0.5rc does not require scsi-emulation, BUT I haven't looked at the multi-session code, which as I recall still uses scsi-emul.
So, will take a look at that now.

If you look at /usr/sbin/createpuppyonline in 1.0.5rc, you will see how burn to cd with cdrecord:

Code: Select all

cdrecord $BURNMULTI -data -eject -v speed=4 dev=ATAPI:$CDR puppy-$RIGHTVER-custom.iso

where CDR="/dev/hdc" or whatever.
BURNMULTI="" or "-multi"

What about growisofs? can it accept something like dev=ATAPI:/dev/hdc?
...what would the format be?

[Ted Dog]

growisofs is multi-session by default. the tricky stuff is there must not be any spaces around the equal sign. to burn an iso. cdrecord is not piped, not needed.

Code: Select all

growisofs -Z $CDR=puppy-$RIGHTVER-custom.iso

It behaves better if growisofs burns files straight to disk, note lack of equal sign.

Code: Select all

growisofs -Z $CDR  -J -R -D -b isolinux.bin -c boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table $WRKDIRECTORY
 

the -pad should be avoided in constructing iso.

this is the code to append from rc.reboot-cd

Code: Select all

growisofs -M $CDR -J -R -D -new-dir-mode 0755 -graft-points -path-list /tmp/listfinalshutdown.txt  

[/code]

[Ted_Dog]

with SCSI on limit 2g

Code: Select all

 echo "Now saving session to burner drive..."
   growisofs -M /dev/scd0 -J -R -D -new-dir-mode 0755 -graft-points -path-list /tmp/listfinalshutdown.txt  
echo "...done"
  fi #ID001

without SCSI limit 4g for last new directory. Data can go to 4.7G physical limit (or over with -overburn )

Code: Select all

  echo "Now saving session to burner drive..."
   growisofs -M /dev/hdb -J -R -D -new-dir-mode 0755 -graft-points -path-list /tmp/listfinalshutdown.txt  
echo "...done"
  fi #ID001

my DVD burner is slave on first ide '/dev/hdb'

[BarryK]

Ted,
In an earlier code example, the growisofs example did not have the "-D" option
-- what does that do?

[Ted Dog]

Code: Select all

   #...see note above. Feeding in filelist this way...
   mkisofs -D -J -R -C $SECT -M $DEV -pad -new-dir-mode 0755 -P "Puppy Linux" -p                      "Barry Kauler" -graft-points -path-list /tmp/listfinalshutdown.txt  $MYDATE/$LO                     G=$LOG | cdrecord -multi -data -eject -v speed=4 gracetime=1 dev=$CDR  -
   #...v1.0.4 added -D option. got deep relocation error for PupGets installed i                     nto /root/.usr/
   #   deep relocation does not work for multisession CDs. -D turns it off, but                      violates ISO9660.
   echo "...done"
  fi

I used it to be consistant with above code. In the first example code no mkisofs options are used since the already exist within the preconstructed ISO file.

[Flash]

Violating iso9660 standard might be acceptable. I only have a hazy notion of how multisession Puppy works, but it seems to me that, except for forensic purposes or the possibility of an undocumented quirk in the CD drive or its firmware, it makes no difference what filesystem multisession Puppy uses on the CD. The multisession CD is completely self-contained; the software that reads the filesystem on the CD, is contained in the OS on the CD.

[Guest]

I think a live-dvd strategy will be a winning combination !

so how does that differ from before?:?

[Perkins]

Yes, you could use any file system you want on the CD. However, a standard file system that can be read by other operating systems is definitely a good thing. It's really handy to be able to read my files from any machine without having to boot puppy.

Back to the original subject of this thread for a moment, I think packet writing would be a nice addition at some point. Theoretically one could then use a CD/DVD RW as a read-write disk drive. So by carrying a live-CD, and another disk, you could have the equivalent of a computer with a harddrive in terms of the space available and the way programs can access the disk.

One would of course have to be careful to keep backups since RW disks do have a finite number of write cycles. But that would be a relatively minor hassle compared to being able to actually have and run large programs without needing huge amounts of memory or access to a harddrive.

[Flash]

...Using puppy version 1.02 the new limit was reached. The DVD very near 4GiB boundry gave a new limit...

See about 3/4 the way down this page; the first entry under "Technical Ramblings."

Perkins, the way I interpret it, this means that the 4GB isofs limit would not exist if multisession DVD Puppy used, say, ext2 filesystem instead of isofs. The isofs addressing limit is really 32 bits, but that still potentially wastes ~500MB of a full-size DVD.

As for being able to access a multisession Puppy DVD on any machine, Windows can't open any file on my multisession Puppy DVD. Anyway, in general I wouldn't want it to be easy for anyone to read what's on my DVD.

Using a DVD as a replacement for a hard drive is problematic because of the limited rewrite lifetime of a DVD. From what I've read, DVDs can only be rewritten around 1000 times in a particular spot. Much better to use flash memory for what amounts to swap memory, since flash can be rewritten around a million times. Some flash filesystems move the writing area around so as to maximize the lifetime of the memory. The same could be done for DVD, but flash memory would still last about a thousand times longer than DVD in that service.

[Ted Dog]

Flash,
How odd, my version of XP service pack2 can read the DVD's just fine. However my laptop (once a ME) has a issue with any CD/DVD with second sessions.

[Flash]

Ted, I'm not sure you understood what I meant. Windows can see the files on the DVD (boot.cat, isolinux.bin, image.gz, etc.,) but can't open them. Also Windows also only sees the first session on the DVD.

[BarryK]

Ted, I'm not sure you understood what I meant. Windows can see the files on the DVD (boot.cat, isolinux.bin, image.gz, etc.,) but can't open them. Also Windows also only sees the first session on the DVD.

But you guys are using DVD-RW or DVD+RW right?
I think someone posted that a DVD-R, Windows can see all the sessions?

For DVD-RW/+RW, it may depend on whether the sessions are saved in
sequential mode or overwrite mode.

[GuestToo]

i think packet writing drivers deliberately fragment files so all the sectors on the disc are used, to maximize the number of writes that can be done ... and flash drives do the same thing

an interesting (Windows only) program that uses packet writing is AccuBurn

it doesn't require any drivers to be installed either to write or to read the discs, like InCD or DirectCD ... the discs it creates can be read on any OS just like an ordinary disc

what it does, is burns cds/dvds a sector at a time, and checks that the sector burned ok ... if it did not burn ok, it doesn't use that sector and burns the sector again, until the sector is burned properly

then, after all the sectors have been burned, it creates and burns the updated Table Of Contents using only the good sectors that were burned

so the burn is usually very reliable

of course, if there is a problem burning the Table Of Contents, you can lose the contents of the disc, just like a regular cd/dvd

because it burns a small packet at a time, it's impossible to have a buffer under-run

the program is very simple to use, just drag files/folders to the window and click the big red Burn button ... everything is automatic, it asks for a new disc if there is not enough room on the disc ... it doesn't need to be configured for your hardware either, it figures out what hardware you have and what options it needs to use, like cd burning speed, automatically

it's good for TC (technologically challenged) people, but i liked using it because it was so simple and easy to use (i like simple)

it has copy protection in it that connects to the internet the first time you install it, which i found slightly annoying

i have not tried the latest version

anyway, just a review of a Windows program some people don't seem to know about (i have no connection with the company other than having used the program) ... if Linux had an open source equivalent of a program like this, it would make cd/dvd burning very easy and reliable for TC people

picture of Accuburn ... all you ever do is drag files/folders to the right window pane and click the red Burn button

more details

[GuesT ed_Dog]

You are correct about the use of W/R-DVDs tried it with DVD-R added pups, configured the way I like it, rebooted DVD, setting reappeared ok. deleted file, and added large package (firefox) rebooted, second settings (firefox icon on rox, file gone) everything perfect, you the man!!!

[Flash]

"...you guys are using DVD-RW or DVD+RW right?
I think someone posted that a DVD-R, Windows can see all the sessions?

For DVD-RW/+RW, it may depend on whether the sessions are saved in
sequential mode or overwrite mode.

I'm using DVD+RW. I wanted to use a reusable DVD for initial testing and that's the reusable DVD I had. I haven't tried multisession Puppy on a DVD-R yet. I figure if DVD+RW works, probably any DVD will work.

If Windows can't open the files on a multisession Puppy DVD, why worry if Windows can see anything on the disk?

Would it be difficult to use one of the native Linux filesystems (ext2, ext3, etc.) instead of isofs for multisession DVD? Hmm, I suppose the name "growisofs" gives a clue.

Barry, this is very preliminary: the 20oct05 version may have a problem using the internet. It configured eth1 with auto DHCP okay, but when I open Mozilla it has trouble loading any website -- only succeeded one or two times, and those took a long time. This may be a bad burn to DVD. I'll burn it to a different disk to confirm there is a problem, and if it repeats I'll burn 19oct05 to the same disk to see if the problem goes away.

[Perkins]

The only reason I was thinking packet writing might be useful Flash, is that 512MB thumb drives are usually around $50 apiece. 650-700MB CD-RWs can be had for $.50 apiece. Factoring in the price of the medium, the difference in cost per writable MB is a factor of less than 10. And if you happen to be running programs that do a lot of reading, and only a little writing it's definitely woth it for the fact that the instantaneous price is lower, because even at only 1000 writes, the CD will last a heck of a long time, and you can afford more of them at once.

Anyway, I'll quit interrupting your discussion.

[Flash]

Anyway, I'll quit interrupting your discussion.

You weren't interrupting me. I was just shooting my mouth off, as usual.

Actually, you bring up an important subject: the cost per MB of flash memory. At some point it may make more sense economically to use flash memory than multisession DVD or CD.

My city library has a lot of audio books on CD. These aren't very rugged and seem to me to be a bad investment. It has occurred to me that if the licencing could be arranged, it might be cheaper in the long run for the library to buy audio books as mp3s, which are loaded onto special flash mp3 players on demand, to loan to library patrons. These mp3 players would be made so that their flash memory could only be read by the internal mp3 player. In other words, the memory would appear to an external computer to be Write-Only Memory, or WOM.

[Perkins]

See, now, that depends. If the audio books spend most of their time on the shelf, then the CDs are probably a better investment. They're less durable, but they're also far cheaper per MB of storage.

For an example where packet writing would be useful, I have a couple large programs that read very large blocks of data and instructions, but only write a few tiny configuration files on occasion. I don't use them very often, so I don't want to spend a lot of money on a flash drive when a $.50 CD will work just as well. Theoretically I could probably trick into storing its config files elsewhere, but that's rather more effort than it would be worth.

Second useful case, there are actually computers out there that don't have USB drives. (I own several. ) Since you have to have a burner to use a Multisession CD anyway... You get the idea.

Now I don't know how large a packet writing module would be, or how hard it would be to include. If it's huge and is a major pain, then don't bother. If it's tiny and easy, then it could be quite a useful thing to have.