eap@BU-IT.BU.EDU (Eric A. Pearce) (05/24/89)
I am thinking of using GNU Tar on a "production" system for backups. I'd be interested in hearing war stories and problems with relying on it for all your backups. I know some of FSF machines use it. Has someone done full restores with it? (I imagine you would have to make your own "miniroot" with GNU tar on it). This would be on an IRIS 4D/GTX (sysV, with bsd extensions) -e ------------------------------------------------------------------------------- Eric Pearce ARPANET eap@bu-it.bu.edu Boston University Information Technology CSNET eap%bu-it@bu-cs 111 Cummington Street JNET jnet%"ep@buenga" Boston MA 02215 UUCP !harvard!bu-cs!bu-it!eap 617-353-2780 voice 617-353-6260 fax BITNET ep@buenga
glenn@eecg.toronto.edu (Glenn Mackintosh) (05/26/89)
In article <8905232207.AA18283@bu-it.BU.EDU> eap@BU-IT.BU.EDU (Eric A. Pearce) writes: > > I am thinking of using GNU Tar on a "production" system for backups. > I'd be interested in hearing war stories and problems with relying > on it for all your backups. I know some of FSF machines use it. > Has someone done full restores with it? (I imagine you would have to > make your own "miniroot" with GNU tar on it). I have not used it for backups myself, but one thing to watch out for is that tar images of things like dbm files can cause you some problems. DBM files do not actually take up as much real disc space as they claim to when you do an ls -l. This is do to the fact that they have empty blocks in their inode block list which don't have real disk pages associated with them since they never get referenced. You can see this if you look at the difference between what ls -l and ls -s say the file sizes are. For example: -rw-r--r-- 1 root 217088 May 25 15:12 /etc/yp/csri/passwd.byuid.pag 152 /etc/yp/csri/passwd.byuid.pag 152 * 512 = 77824 If you copy the file these pages will get filled in. Likewise tar does not know about these holes and fills them in. In fact even if tar did try to recognize these big blocks of zero's it could do nothing about it. I have thought about fixing this problem but it would require a pretty nonstandard change to the record structure. There are other ways to get files like this as well, so just because you don't have dbm files does not mean you might not experience the problem. A sparse file can be created by a buggy program or by a user: $ adb -w bigfile 0t100000000?w0 ^D $ ls -ls bigfile 24 -rw-r--r-- 1 glenn 100000004 Jan 3 17:59 bigfile This file is really only about 24k in size but takes up 100M on a tar backup. Glenn Mackintosh Univ. of Toronto CSNET/ARPA: glenn@eecg.toronto.edu UUCP: UUNET!utai!eecg!glenn CDNNET: glenn@eecg.toronto.cdn BITNET: glenn@eecg.utoronto.bitnet (may not work from all sites)
bart@videovax.tv.Tek.com (Bart Massey) (05/26/89)
In article <8905232207.AA18283@bu-it.BU.EDU> eap@BU-IT.BU.EDU (Eric A. Pearce) writes: > > I am thinking of using GNU Tar on a "production" system for backups. > I'd be interested in hearing war stories and problems with relying > on it for all your backups. I know some of FSF machines use it. The version I'm currently using (1.05) has a memory leak which kills it on our VAX (a VAX750 running 4.3 Tahoe with about 30M of VM and 1.5G of files to back up) way into a full level 0 dump. I don't know yet if later versions have the same problem, and I haven't had time to diagnose and fix it. I posted some bugfixes and enhancements to this group a bit ago -- see that article for details... Once I get it debugged, we will be relying on it for all our backups on this machine -- it's features are just what I want. Bart Massey TV Systems Engineering M.S. 58-639 627-5320 bart@videovax.tv.tek.com
seg@smsdpg.uu.net (Scott Garfinkle) (05/28/89)
> From article <8905232207.AA18283@bu-it.BU.EDU> eap@BU-IT.BU.EDU (Eric A. Pearce): > > I am thinking of using GNU Tar on a "production" system for backups. > I'd be interested in hearing war stories and problems with relying > on it for all your backups. I know some of FSF machines use it. Only possible bug: On my HP9000/300 running HPUX 6.5, Gnu tar doesn't seem to notice when an NFS-mounted volume starts, and tries to dump this stuff, too. I'll probably have to investigate this....