KHB: A Filesystems reading list [LWN.net]

KHB: A Filesystems reading list

Posted Aug 22, 2006 23:25 UTC (Tue) by nlucas (subscriber, #33793) [Link]

CD-RW et al are what UFS is designed for.

Yes I know, but last I checked it's read-only, i.e. you can't use it on a partition as a normal filesystem, like the old msdos filesystem.

You have no easy way (AFAIK) to just add a file to a DVD-RW, like copy/paste or drag a file to a DVD-RW folder.

I would be happy enough when I can do something like this from the command line:

$ ufs-cp somefile.txt /media/cdrw/somedir/

and let it do the rest in the background (and not wait an eternity, off course). Much like the old days with DOS formated floppy disks.

My home PC still have an USB 1.1 hub and so I'm used to wait until it flushes all writes to the USB pen when unmounting. I only ask for something similar for a DVD-RW (the speed should not be that much different than for USB 1.1).

And you have the advantage that you can actually prevent the user from ejecting the CD/DVD before all writes are flushed, so less risk of user generated filesystem corruption (at least for users that don't use that cute little hole to open the "cup-holder" ;-).

KHB: A Filesystems reading list

Posted Aug 23, 2006 1:24 UTC (Wed) by nlucas (subscriber, #33793) [Link]

s/UFS/UDF/

It seemed weird, but followed your path without thinking more about it ;-)

KHB: A Filesystems reading list

Posted Aug 23, 2006 16:34 UTC (Wed) by nix (subscriber, #2304) [Link]

Um. Yes. Brainfart, sorry.

KHB: A Filesystems reading list

Posted Aug 23, 2006 16:37 UTC (Wed) by nix (subscriber, #2304) [Link]

What? Packet-written CD-RWs use UDF filesystems, and act just like a normal filesystem (except that the device is really rather slow and the filesystem overhead is ridiculous). In modern CD-RWs and all DVD-RWs this is even in hardware (while I haven't yet seen a CD rewriter that has packet-writing firmware that works well, this may not be true of DVD-RW drives).

It's ISO-9660 that has to be built in one lump.

KHB: A Filesystems reading list

Posted Aug 24, 2006 21:51 UTC (Thu) by nlucas (subscriber, #33793) [Link]

I now understand the problem has nothing to do with filesystems, except the UDF overhead problem (and ISO-9660 compatibilty), as it's the only usable CD/DVD RW filesystem (because it can be read everywhere).

It seems the problem is only on the software side (for modern RW drives, I mean), and maybe cdrecord "flame wars" have delayed the adoption of a standard linux solution for the typical user cases (like maybe a FUSE DVD UDF filesystem that works the same as a USB pen, i.e. can add/delete files on the fly).

Well, I still have a lot of doubts about the process, but the truth is this thread is becoming off topic so I'll refrain my thoughts for latter times.

KHB: A Filesystems reading list

Posted Aug 27, 2006 15:53 UTC (Sun) by nix (subscriber, #2304) [Link]

We already have exactly that feature: the packet-writing driver. If you're
packet-writing to CD-RW (or DVD-RW) you don't *need* cdrecord, or FUSE.

(It does indeed have significant overhead, as you say.)

KHB: A Filesystems reading list

Posted Aug 24, 2006 2:12 UTC (Thu) by wookey (subscriber, #5501) [Link]

growisofs meets your command line criteria, I think.

growisofs -M /dev/dvd files

will add files to a disk (CD or DVD).

KHB: A Filesystems reading list

Posted Aug 24, 2006 7:36 UTC (Thu) by drag (subscriber, #31333) [Link]

growisofs even supports pipes...

My favorite backup technic for my own home directory is to use growisofs with splitpipe.

Splitpipe is a nice utility that splits files just like 'split' does, but it performs a action on each section it makes.

Check it out:
tar c /home | splitpipe -s dvd -o 'growisofs -Z /dev/dvd=/dev/stdin'

It'll burn a DVD until it gets finished, pause, prompt you for you to press enter so you can have time to pop in a new DVD and off you go.

Then they have a 'joinpipe' command for rebuilding the data.

Supports md5sum'ng the data and makes sure you don't accidently try to join the data back together in the wrong order and such.

Of course if you have a file that is less then 4 megs you could just go:

cat filenmae |growisofs -Z /dev/dvd -

And I think that should work out fine. Then you should be able to 'cat /dev/dvd > whatnot' to get it back.

Haven't tried it personally like that, but I expect it to work fine.

KHB: A Filesystems reading list

Posted Aug 24, 2006 21:57 UTC (Thu) by nlucas (subscriber, #33793) [Link]

I'm almost certain I had read the growisofs manual page some moons ago, but somehow missed that command.

Thanks for the heads-up. I'm an happier man now :-)