Path: utzoo!utgpu!water!watmath!mks!wheels From: wheels@mks.UUCP (Gerry Wheeler) Newsgroups: comp.sys.ibm.pc Subject: Re: ARC Wars Message-ID: <507@mks.UUCP> Date: 19 Sep 88 20:59:56 GMT References: <1653@dataio.Data-IO.COM> <360004@hpbsla.HP.COM> Organization: Mortice Kern Systems, Waterloo, Ont. Lines: 37 In article <360004@hpbsla.HP.COM>, campbell@hpbsla.HP.COM (gary campbell) writes: > I would like an archiver with compression that can handle multi-floppy > archives, primarily as a means of system backup. Something which fits that description is the cpio utility in the MKS Toolkit. It is not, however, freeware. On Unix, one would use a command like "find /usr | cpio -ocv | compress >/dev/xxx". On DOS, of course, because there are no real pipes, the entire output of cpio would be saved in a temp file before compress was run. This doesn't work well if you are trying to back up 10 megs of data. :-) So, we added an option to cpio to have it do the compression on the fly. The results are the same as above, but no pipe is involved. Our cpio will also assume that a write error indicates a full disk, and asks if you want to continue on another volume. This allows the cpio file occupy as many floppies as necessary. > Someone on a local BBS made the following comments about compression in > a backup utility: "Also, you would have to wonder about the integrity > of the backed-up files. If the archive dropped one bit -- it could > destroy multiple files within the one archive.". True. You don't want to use compression if your floppies are flakey. (But who would use flakey floppies for backup?) If you're going to start from scratch and create a backup program with compression, you probably want to compress each file separately and try to arrange some way to re-synchronize to the headers within the file in case there is some corruption. Possibly the use of a separate file with pointers into the backup file would work. Or, perhaps the indexes could be stored at the end of the file in a fixed size area. (Not too handy on a multi-volume backup, though.) -- Gerry Wheeler Phone: (519)884-2251 Mortice Kern Systems Inc. UUCP: uunet!watmath!mks!wheels 35 King St. North BIX: join mks Waterloo, Ontario N2J 2W9 CompuServe: 73260,1043