>The actual reasons why one might prefer tar to dump are that tar is 
>cross-platform ...
>... and tar allows   you to make backups of arbitrary (sub-)directory
>trees instead of entire filesystems.

In addition to that, the reason tar is **strongly** pushed on Linux is
that dump works with the raw disks while tar goes through the file system
to get its data.  The more aggressive the OS is about caching file data
(and metadata) in memory (which Linux tries very hard to do), the less
likely it is the raw disk has the "real" data, or at least a consistent
version of it.

Linus sent out a pretty firm "you should never use dump" E-mail quite
a while back.

On the other hand ...

I don't (didn't) use tar at Purdue, in general, because it changes the
access time on the files it backs up.  That's a very bad thing.

If you're about to mention --atime-preserve, don't :-).  Setting that
flag causes the change time to be altered.

Our workaround was to use a GNU tar wrapper (2000+ lines of finely crafted
Perl) for LVM volumes that created a snapshot and backed that up.  We just
ignored the access time problem for file systems not under LVM control.

>Toomas Aas

John R. Jackson, Senior Systems Analyst, Engineering Solutions, Inc