On Tue, Dec 23, 2003 at 11:42:14AM -0500, Henson, George Mr JMLFDC wrote:
> What are the advantages or disadvantages to using tar instead
> of dump?
(This is partially brief repetition, but also contains new
points.)
In dump's favour:
- The estimate phase is faster
- It doesn't change any of the timestamps of files it's backing
up (tar doesn't change mtime either of course, but can't
avoid changing either atime or ctime (actually, I recently
read that Solaris provides a way, if you're root, but I don't
know whether GNU tar takes advantage of it)
- You can do interactive restores natively. (amrecover gives
you the same functionality, regardless of dump vs. tar, so
this difference *only* applies if Amanda isn't in the loop at
restore time, or if you don't have the index files, which
amrecover requires.)
- Dump programs are customized to the local file system's
idiosyncracies. I'm guessing (but don't know) that this
means that dump can back up system-dependent metadata that
tar has no clue about (ACLs, Linux ext2 "chattr" flags,
FreeBSD's "chflags" variant thereof, and the like)
In tar's favour:
- You can exclude files
- You can split a partition into multiple DLE's. This is
necessary if you have partitions larger than will fit on a
single tape, since Amanda can't split a single dump onto
multiple tapes (not yet anyway; work is in progress,
hooray!).
- Dump is reported to be undependable on Linux -- Linus says
so, anyway. (He has a thing against dump, so doesn't see
that as a problem, but IMO it's because Linux has deviated
from standard UNIX in undesirable ways. Regardless of blame,
though, it's an issue to be dealt with.)
- Backups are portable. The downside of every dump being
customized to its file system is that you very likely can't
restore a dump from platform X using platform Y's "restore".
I've never tried cross-file-system restores on the same box
(restoring from a Solaris VXFS dump onto a Solaris ufs
partition, for example), but I imagine that whether you can
get away with it depends on the specific combination and the
specific platform.
--
| | /\
|-_|/ > Eric Siegerman, Toronto, Ont.[EMAIL PROTECTED]
| | /
It must be said that they would have sounded better if the singer
wouldn't throw his fellow band members to the ground and toss the
drum kit around during songs.
- Patrick Lenneau