Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!uunet!pdn!tscs!tct!chip From: chip@tct.uucp (Chip Salzenberg) Newsgroups: comp.unix.questions Subject: Re: Backups using compress Message-ID: <275BF2FA.68AF@tct.uucp> Date: 4 Dec 90 19:03:22 GMT References: <11389:Nov3010:16:4190@kramden.acf.nyu.edu> <275A875A.3AB0@tct.uucp> <26547:Dec404:51:1690@kramden.acf.nyu.edu> Organization: Teltronics/TCT, Sarasota, FL Lines: 29 According to brnstnd@kramden.acf.nyu.edu (Dan Bernstein): >In article <275A875A.3AB0@tct.uucp> chip@tct.uucp (Chip Salzenberg) writes: >>Sure, error correction is very nice. But sometimes data are lost, >>period, no recourse, from the *middle* of a backup. > >So what? Do you mean to say that error-correcting codes can't correct >errors? I meant "loss despite best efforts at error correction." Obviously, error-correcting codes can't fix everything. If I lose a few bytes in a tape block, then depending on the method used, I'm probably covered. But if a media defect spans three tape blocks, those data are *gone*. Furthermore, as I wrote (but was not quoted by Dan): >>If you've compressed individual files, at least you can recover the >>files on the untrashed portions of the archive, both before and after >>the point of failure. So you see, Dan, I am not attempting to proscribe compression during archiving. Rather, I am putting forth the position that files should be compressed individually as they are archived, instead of having the archive compressed as a whole. This approach gains tape real estate while minimizing the damage caused by dropped data in the middle of an archive. -- Chip Salzenberg at Teltronics/TCT , "I'm really sorry I feel this need to insult some people..." -- John F. Haugh II (He thinks HE'S sorry?)