Hi, > I use a 10GB HP Colorado tape drive to backup my personal Linux PC > every week/month. I backup to the tape using GNU tar in compress mode, > thereby allowing me to back up to approximately 20GB of files. > > The closest alternative to the 10GB tape is the 8.5GB DVD-RW DL (i.e. > dual layer). The capacity should be good enough for my needs. > > I can't write to a file on hard disk and afterwards burn the DVD as I > do not have enough disk space. So, I am thinking of using the kernel's > packet writing abilities to do my backups.
This list is probably not the right point to find expertise about the packet interface and UDF. We are more into burn programs which write whole sessions in a single sweep. Linux packet writing relies on a particular write strategy which is not necessarily available with all media types or media states. Wether it will work with DVD-RW DL is a matter of trying out. Tell us, so we can tell the next one. Are there really -RW DLs ? MMC-5 lists DVD+R DL, DVD-R DL, DVD+RW DL. I never saw DVD+RW DL on sale, btw. The fact that you will be writing your archive on-the-fly is not necessarily an obstacle to our style of burning. The typical problem with that is that some programs with some media demand a predicted size. But with few media types and states this size prediction is really inavoidable. If your media supports packet writing then i am quite sure it will do writing on the fly via program growisofs. Like tar -jcf - * | \ growisofs -Z /dev/hdc=/dev/fd/0 (/dev/hdc is the target drive, /dev/fd/0 is standard input to be used as data source.) You need no other preparations for that. The tar archive can later be read from not mounted /dev/hdc like from a tape at /dev/mt0. Maybe you get error messages about an unclean end of archive because of extra bytes. (afio and star archives do better.) If it turns out that DL media are not suitable then i would advise you to use DVD+RW. It is not too hard to split a tar archive over several media but i am more in favor of producing an independent archive per media. For that i have my own backup tool scdbackup which can produce afio or star archives and puts them on a set of media (CD, DVD, ...). growisofs is used as burn program for DVD media. Since the size is unpredictable it is estimated cautiously and an eventual overrun is handled by writing the rest to another media. It is also able to make one big archive which gets split over several media. But reading those is cumbersome because you have to read the whole media set in order to access a file on the last media. For quickest file access i prefer scdbackup's ISO-9660 formatted output. This cannot be compressed but if you need to access a single file it is unbeatably convenient. If you backup whole partitions or exotic file types, i would advise to use afio or star format. Many media types do not produce a neat End-Of-Media event. So the archive formats have to provide own means to detect their End-Of-Archive. To my experience GNU-tar fails to do so. That's why i deem afio and star more suitable. Each of them has its strengths: afio -Z has its archive structure uncompressed but the files are compressed. This allows to recover sane parts of damaged compressed archives. star is very complete when it comes to file types and sizes. I use it for system snapshots made from single user mode or a booted rescue system. Restore works like that: boot rescue system, make empty filesystem, unpack archives to filesystem, eventually update boot loader (run /usr/sbin/lilo), boot. (Of course this works only if you can continue using your old system hardware configuration.) I never challenged afio like that. It is not outruled that i produces sufficiently complete system snapshots too. Have a nice day :) Thomas -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
