Testing Tar (was Re: bad news for bsdtar..)

[Richard Coleman]

Don Lewis wrote:
>>>At least the -current version of tar skips reading the
>>>data when it is writing to /dev/null.
>>
>>A-ha!  That explains a few of the odd timings I've seen.
>>I wonder why it does that?  (Other than to look good on
>>benchmarks, of course. ;-)
> 
> 
> This speeds up Amanda quite a bit.  Amanda will run tar with the
> --totals option as well as other options to specify either full or
> incremental backups multiple times for each file system that it backs
> up.  It does this to plan the best mixture of full and incremental
> backups.  If tar actually read the data from disk each time, the
> planning phase would take a *lot* longer, and would thrash the disk a
> lot more.

Until libarchive gets support for sparse files, it's probably better to 
stick with gtar or rdump with Amanda.

But the concept of a version of Amanda that natively uses libarchive is 
very cool.  It seems like a natural target.

Richard Coleman
richardcoleman at mindspring.com