kjh@pollux.usc.edu (Kenneth J. Hendrickson) (11/29/90)
If you do a backup with tar, and pipe the output through compress before writing it on the disk or tape, and ... if there is a single bit error on the tape, then you could loose all the files in your backup from that point until the end. If you don't use compress, and there is a single bit error, you won't have that problem, but you will require many more disks or tapes. -- So what do people do? Do you trust your disks/tapes and use compress? -- favourite oxymorons: student athlete, honest politician, civil war Ken Hendrickson N8DGN/6 kjh@usc.edu ...!uunet!usc!pollux!kjh
tneff@bfmny0.BFM.COM (Tom Neff) (11/30/90)
In article <28498@usc> kjh@pollux.usc.edu (Kenneth J. Hendrickson) writes: >If you do a backup with tar, and pipe the output through compress before >writing it on the disk or tape, and ... If there is a single bit error >on the tape, then you could loose all the files in your backup from that >point until the end. If you don't use compress, and there is a single >bit error, you won't have that problem, but you will require many more >disks or tapes. So what do people do? Do you trust your disks/tapes >and use compress? I use compress but do a verify read of the tape after the run. (What else has my system got to do at 3am.) If the verify fails, I hear about it next morning. That's enough warning to retire the old tape and re-run. For me, compress is definitely worth it.
lerman@stpstn.UUCP (Ken Lerman) (12/02/90)
In article <28498@usc> kjh@pollux.usc.edu (Kenneth J. Hendrickson) writes:
->If you do a backup with tar, and pipe the output through compress before
->writing it on the disk or tape, and ...
->
-> if there is a single bit error on the tape,
-> then you could loose all the files in your backup from that
-> point until the end.
->
->If you don't use compress, and there is a single bit error, you won't
->have that problem, but you will require many more disks or tapes.
->
->--
->
->So what do people do? Do you trust your disks/tapes and use compress?
->
->--
-> favourite oxymorons: student athlete, honest politician, civil war
->Ken Hendrickson N8DGN/6 kjh@usc.edu ...!uunet!usc!pollux!kjh
Of course, an alternative is to compress your files first and then
backup using tar.
I would not consider a compressed tar file to be a viable backup.
So far, everything fits on one tape on my machine.
Kenfriedl@mtndew.Tustin.CA.US (Stephen J. Friedl) (12/03/90)
In article <28498@usc>, kjh@pollux.usc.edu (Kenneth J. Hendrickson) writes: > > if there is a single bit error on the tape, > then you could loose all the files in your backup from that > point until the end. > > So what do people do? Do you trust your disks/tapes and use compress? Some types of data lend themselves to a compress backup better than others. Several of my customers, for instance, do backups of databases (a few very large files) where the entire backup must be readable for any part of it to be useful (lots of related files). If you have an error in any file, the entire backup is bad whether compression is used or not. Steve -- Stephen J. Friedl, KA8CMY / 3B2-kind-of-guy / Tustin, CA / 3B2-kind-of-guy +1 714 544 6561 / friedl@mtndew.Tustin.CA.US / {uunet,attmail}!mtndew!friedl "If it doesn't core dump, ship it" - Gary W. Keefe, on product development
guy@contact.uucp (Guy Lemieux) (12/03/90)
In <5875@stpstn.UUCP> lerman@stpstn.UUCP (Ken Lerman) writes: >In article <28498@usc> kjh@pollux.usc.edu (Kenneth J. Hendrickson) writes: >->If you do a backup with tar, and pipe the output through compress before >->writing it on the disk or tape, and ... >-> >-> if there is a single bit error on the tape, >-> then you could loose all the files in your backup from that >-> point until the end. >-> >->If you don't use compress, and there is a single bit error, you won't >->have that problem, but you will require many more disks or tapes. >-> >->-- >-> >->So what do people do? Do you trust your disks/tapes and use compress? >-> >->-- >-> favourite oxymorons: student athlete, honest politician, civil war >->Ken Hendrickson N8DGN/6 kjh@usc.edu ...!uunet!usc!pollux!kjh >Of course, an alternative is to compress your files first and then >backup using tar. >I would not consider a compressed tar file to be a viable backup. Another alternative is to tar groups of files into one file on the hard disk, compress the tar file, and then tar the resultant file.tar.Z. Just my $0.02 -- Guy Lemieux ENG SCI University of Toronto guy@contact.uucp 9 T 2 Faculty of Applied Science and Engineering -- As they say about Intel's brilliant efforts at fudging benchmarks: -- "If these guys are so smart, why don't they just make faster machines?"