The hidden email

Robert Brockway rbrockway-wgAaPJgzrDxH4x6Dk/4f9A at public.gmane.org
Wed Oct 19 18:59:33 UTC 2005


On Thu, 13 Oct 2005, Lennart Sorensen wrote:

> I use afio rather than tar/gzip since afio compresses each file in the
> archive with gzip rather than creating the archive and then compressing
> it.  You loose some compression as a result but not much, but you gain
> the ability to quickly seek through the file to the head for the file
> you want and then start decompressing the file (and only the file)
> rather than having to decompress the whole thing to find the header and

This approach (also taken by the zip algorithm) provides for improved data 
reliability too.

If you use tar.gz ("archive then compress") to dump data to a tape and the 
archive suffers from an error on restore your archive is basically toast.  
You may have archive restore utilities available if you are lucky.

If you use a "compress then archive" approach (used by afio and zip) you 
will only lose a minority of files if you suffer an error when restoring.

When it comes to tape technologies that are not as reliable as many people 
think this is a big deal.

Like many sysadmins I never use "archive then compress" to tape but I use 
it on harddrives all the time as the level of reliability is much greater.

Rob

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