SASQUATCH@ALBION.BITNET ("Kevin O. Lepard 629-5511 x6668", 517) (03/20/89)
I've used Shrinkit to archive a bunch of files, and a though just occurred to me. If something happens to the file (say a block or half a block goes bad for some reason) will I lose _everything_ in the archive or just the file(s) that were in that block? I assume that it would depend on _which_ part of the file got damaged, but I want to be sure. Thanks in advance. Kevin Lepard Bitnet: Sasquatch@albion.bitnet
nicholaA@moravian.EDU (03/23/89)
>I've used Shrinkit to archive a bunch of files, and a though just occurred to >me. If something happens to the file (say a block or half a block goes bad >for some reason) will I lose _everything_ in the archive or just the file(s) >that were in that block? If the bad block occurs in the middle of a data section, the single record that the bad block occurred in will be damaged, but the rest of the archive would be OK. Even though ShrinkIT might stop once it got the IO error after reading that bad block, you could still selectively extract the files AFTER the bad record. *IF* the bad block just *HAPPENS* to fall on top of a header of a record, that is bad indeed because the headers act akin to a linked list. If one of the links gets destroyed, the rest of the archive isn't worth much. Jason Blochowiak and myself have discussed writing a sort of "archive recoverer" which would search through a file that was a damaged NuFX archive and try to re-construct it, much the way Glen Bredon's "Mr. Fixit" program is supposed to work on ProDOS disks. andy >Kevin Lepard >Bitnet: Sasquatch@albion.bitnet > ---- Andy Nicholas CsNET: shrinkit@moravian.edu Box 435, Moravian College InterNET: shrinkit%moravian.edu@relay.cs.net Bethlehem, PA 18018 liberty!batman!shrinkit@sun.com ---- UUCP: rutgers!lafcol!lehi3b15!mc70!shrinkit I have a CD player, send CD's. rutgers!liberty!batman!shrinkit I have a IIgs, send a GS+. ALink PE: shrinkit
lwv@n8emr.UUCP (Larry W. Virden) (03/24/89)
Recently in a few other places (I THINK it was either on Compuserve or over in comp.binaries.ibm.pc.d) I have been seeing some discussion on the next generation of archivers in the MSDOS world. Apparently using some multi directional cross sums (???) a software technique is being developed to include in minimal number of bytes enough info to allow reconstruction of lost data. If this is indeed the case, it sounds very exciting. The ability to have high quality compression AND data reconstruction, while of course highly desireable, hasnt been widely available in the micro realm. Perhaps if some of you folks are familar with the techniques you could share them with us, so that those writing things like dearcs, shrinkits, etc. could learn. -- Larry W. Virden 674 Falls Place, Reynoldsburg, OH 43068 (614) 864-8817 75046,606 (CIS) ; LVirden (ALPE) ; osu-cis!n8emr!lwv (UUCP) osu-cis!n8emr!lwv@TUT.CIS.OHIO-STATE.EDU (INTERNET) The world's not inherited from our parents, but borrowed from our children.