[LUNI] Incremental Tar

[Steven Lembark]

-- "Matt T." <matt at abernackie.com>

> Hi,
>
> 	I was curious if anyone had experience with tar incremental backups?
> Basically the information im looking for is what/how does GNU tar
> define what and how an incremental backup is done? ie.. Are only modified
> files updated in the tar archive? or are the modified files appended to
> the  current archive?
>
> Is cpio a better alternative?..

Tar is a wonderful solution for systems with higher
tape capacity than disk storage and where the cost of
moving data onto and off of the tape is less than having
to position it on disk blocks. It's use of 10K blocks is
also a good choice for your 9-track, reel-to-reel unit
especially since core [remember ferrite beads?] limits
your I/O buffer size so severly that even this much data
movement can lock up a system.

If you have a PDP with drum disk and about 64K of ferrite
core or ttl logic boards then by all means this scenario
fits you :-)

For the rest of us, cpio will generatll be a better backup
solution since it does not fix the tape block size, handles
tape I/O errors quite a bit more gracefully, and can manage
partial backups with simpler procedures (find being the most
obvious/common, perl being another). Since gnu cpio will
happily/automiatcally read tar-format archives, it also works
nicely as a general restore utility.

If it's any indication, Sun's dump has been a front end to
cpio for 10+ years.

--
Steven Lembark                               2930 W. Palmer
Workhorse Computing                       Chicago, IL 60647
                                            +1 888 359 3508