Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!emory!att!linac!midway!gargoyle!chinet!les
From: les@chinet.chi.il.us (Leslie Mikesell)
Newsgroups: comp.unix.questions
Subject: Re: Backups using compress
Message-ID: <1990Nov27.191110.5314@chinet.chi.il.us>
Date: 27 Nov 90 19:11:10 GMT
References: <25106@adm.brl.mil> <14582@smoke.brl.mil>
Organization: Chinet - Public Access UNIX
Lines: 23

In article <14582@smoke.brl.mil> gwyn@smoke.brl.mil (Doug Gwyn) writes:

>>Does anyone know of a way to compress files before sending them through 
>>cpio or tar to tape without actually creating a ".Z" file on disk.

>No, because cpio and tar open the files individually and have no provisions
>for per-file filtration.  What most people do is to compress the archive,
>not the individual files; that also should generally be more compact.
>In this method you can simply pipe the archive through "compress".

There are 2 problems with this method, though.  If you have a single
media error anywhere in the archive it will be pretty much impossible
to recover any of it past the error, and if most of the files on the
disk were already compressed the output may actually expand when
piped through compress.

Has anyone worked on a "packetizing" version of compress that would
be able to pass chunks that would not compress any further through
unchanged (except for a packet header) and provide identifiable
restart points that could be used for error recovery?

Les Mikesell
  les@chinet.chi.il.us