Re: what difference xorriso is it going to make on the user interface?

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

> If you imagine the difference between
> xorriso and older utilities, what do you think is the main difference that
> can be reflected on the user experience? That is, what difference does it
> make if a desktop DVD burning application make use of xorriso that it can
> offer a unique feature or competition advantage over others?

The combination of mkisofs, cdrecord and growisofs still covers most
needs of the users. One needs to know the particular properties of the
various media types, though.

I consider xorriso to be more consistent in its unified view on all
kinds of storage media: CD, DVD, BD, block devices, disk files,
character devices, pipes.
This advantage is best visible if one uses its own commands rather than
the emulations of mkisofs and cdrecord. Nevertheless, the cdrecord
emulation extends the CD multi-session model for ISO 9660 images to
nearly all DVD types and to both BD types. (Use option
--grow_overwriteable_iso)

xorriso covers the whole life cycle of an ISO image:
Creation, expansion, manipulation, extraction of files.
It lists the existing sessions and helps with mounting any of
them on Linux and FreeBSD. (Solaris is incapable in some cases.) 

It has strong extra features for data backup.
- MD5 checksums of each data file and of the whole session. It has
  commands for verifying the checksums and for printing them. 
- Incremental backups may be based either on inode+time, MD5, or
  plain comparison of file contents.
- Transparent zisofs compression (readable on Linux only).
- Visible gzip compression.
- External filter programs for other compression or encryption.
  (Quite slow due to forking the filter processes twice per
   filtered data file.)
- Recording and restoring of Linux ACLs and Linux xattr.
- Fast mass extraction of files without rattling the DVD drive.

xorriso is prepared to serve as slave process under a frontend
program. Its options -dialog, -mark and -pkt_output allow the master
to send commands into xorriso's stdin and to receive their results
and messages from xorriso's stdout.

Last but not least, i try to offer user-friendly support. :))


> Can you think of a few example of such use cases?

I have two backup scripts. One for safely stored DVDs and BDs,
the other for an 8 GB USB stick which i carry with me.

The USB stick backup has its files compressed and encrypted, because
it might get lost on the street. File names and attributes are not
encrypted. This allows to mount the stick and to copy the encrypted
files on about any computer. The backup contains an unecnrypted
copy of the Linux decryption binary and also an unencrypted source tarball
of that program. So i'd need only a Unix system and the pass phrase to
recover my backup.
On the other hand, a cleartext directory tree might reveil information
that should better stay private. One has to weigh, whether this is a
problem or not.

These backups cover about 2 GB of data. A DVD+RW can take about 25
incremental update sessions. A BD is good for about 300 sessions.
The USB stick can take about 200 ones with compressed files.
The Volume Id of each session gives the backup timestamp:

  TOC layout   : Idx ,  sbsector ,       Size , Volume Id
  ISO session  :   1 ,        32 ,   1107596s , HOME_2011_04_02_230358
  ISO session  :   2 ,   1107648 ,     93579s , HOME_2011_04_09_230608
  ISO session  :   3 ,   1201248 ,     81831s , HOME_2011_04_16_215808
  ISO session  :   4 ,   1283104 ,     73907s , HOME_2011_04_23_225250
  ISO session  :   5 ,   1357024 ,     63624s , HOME_2011_04_30_224618
  ISO session  :   6 ,   1420672 ,     64155s , HOME_2011_05_07_080810
  Media summary: 6 sessions, 1484692 data blocks, 2900m data, 1583m free

Although the add-on sessions are small, they show complete snapshots
of the 2 GB backup area.

For details see man xorriso, section EXAMPLES, "Incremental backup of
a few directory trees".


For large backups i use my frontend tool scdbackup
  http://scdbackup.sourceforge.net/main_eng.html
which composes one or more volumes and prompts the user for media.
It is capable of incremental backups too, but other than xorriso
it maintains a separate model of the backup on hard disk.
scdbackup may use xorriso as ISO 9660 formatter and burn program.


Have a nice day :)

Thomas