I've been seeing posters in comp.os.linux.hardware almost exclusively
referring to 'tar' as the way they are doing system backups to tape.
Though I'm fairly new to Linux I've done UNIX sysadmin for years
and have always used 'dump' instead of 'tar'. I suppose that some of
the reasons I don't use tar are probably historical -- old tar
implementations barfed on really long filenames as well as not knowing
about filesystem boundaries. Even with the newfangled GNU tar
features, I still see that dump/restore may have a couple advantages
dump uses a master/slave arrangement when writing tapes which (I
believe) helps to keep the tape buffers full which leads to better
streaming behavior and thus possibly better performance on the tape
dump seems to be somewhat faster if the output device isn't the
major limiting factor, such as when using tar or dump to move files
from one partition to another. In some brief tests on a (P166,
2.0.10, AHA2940U) alternately dumping and taring a 200M filesystem
onto a disk file (on a separate scsi drive) using the '-f' flag I
found that tar was consistently slower on the order of 20-30%. I
don't have a tape drive handy right now to do testing, but I suspect
that some of these factors could lead to improved performance on
dump writes a file table at the beginning of the dump which allows
you to look at the archive contents without having to read the whole
file. The 'restore' command also has an interactive mode which
allows for fast, easy and selective rest*of files.
dump also has rudimentary concept of incremental backups and
optionally keeps track of backup dates its own simple database.
As I said above I'm fairly new to Linux so there may be aspects of tar
and dump under Linux which I don't grasp, but it seems to me that
folks should check out the features of dump to see if they don't
better meet their backup needs.
One caveat though, I needed to recompile dump to get it to work
consistently under 2.0.x. There were problems with the communication
between the master and slave during some dumps which would cause the
dump to fail. Never did figure-out the root cause, but recompiling
has seemingly fixed it.