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

[Don Lewis]

On 24 Apr, Richard Coleman wrote:
> 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.

The incremental backup capabilities that gtar has would be a lot more
useful for Amanda than sparse file support.

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

Especially with ACL support.