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From: j@narcisa.sax.de (J Wunsch)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Floppy-based tape drive questions.
Date: 31 May 1995 11:24:35 +0200
Organization: Private U**x site, Dresden.
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Message-ID: <3qhckj$hpf@bonnie.tcd-dresden.de>
References: <kientzleD97Cru.3nw@netcom.com>
Reply-To: joerg_wunsch@uriah.heep.sax.de
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<kientzle@netcom.com> wrote:
>... However, I know next to nothing about
>floppy-interface tape drives (which is what I'd almost certainly end
>up buying).
Be warned however, that the ft driver maintainer for FreeBSD himself
does _not_ recommend people using floppy tapes. If you can afford
some sort of SCSI tape (perhaps even a second-hand QIC-150 one), get
this instead. It might save you headaches, and it's guaranteed to
work. (For floppy tapes, it _might_ work fine, but it might also
totally fail, depending on what you're buying. And even if it's
working, you'll still suffering from several deficiencies due to the
cheap hardware. SCSI tapes do much more within their own hardware,
which must be done from the CPU for floppy tapes.)
>3) What's a good choice for backup software? What are the pros and cons
> of `dump' vs. `tar'?
In addition to what Terry has already explained, let me tell'ya some
reasons for using `dump' for regularly backups:
. It handles multi-level incremental dumps. This is particularly
useful if you have some partitions which require multiple volumes
and/or a huge amount of time to be backed up. (I think, GNU tar
does also support a two-level backup, but dump's features are much
finer.)
. It stores the table of contents at the beginning of the first
volume, so you don't need to dig through 5 tapes in order to know
if a particular file is on your backup set. For all restore
operations, it first reads this TOC, and remembers it throughout
the operation. Hence it can stop once it knows that all
interesting files have been found (as opposed to tar, which always
reads everything), and it will read only what's absolutely needed
if you're for example restoring a single file out of a set of five
tapes.
. `restore' provides a couple of different restoration methods. One
of them is compatible with the `tar' way. It's normally used if
you're seeking for some lost file (e.g. due to user error). The
other mode is used to restore a partition from scratch. It can
take care for incremental backups, and even deletes the files which
disappeared between the level 0 and the succeeding levels.
Consider the following (as it once occured to me):
o 800 MB partition, 770 MB full, level 0 back up to 4 tapes
o > 100 MB files deleted, in order to make space for another 100 MB
of new files
o level 8 backup done, 1 tape, ~ 100 MB
o partition destroyed (pilot error)
o newfs again
o restore level 0 dump
o restore level 8 dump
With tar, the last step would have overflown the (already almost
full) partition. With "restore r", everything worked well.
. `restore' provides yet another mode. It's a combination of "t"
(list table of contents) and "x" (extract). `restore' reads the
TOC, and offers a shell-like command interface, where you can walk
up and down the file system hierarchy and select those parts of
the hierarchy you wish to have restored later. Very convenient
if you have to select several items from all over the place.
--
cheers, J"org private: joerg_wunsch@uriah.heep.sax.de
http://www.sax.de/~joerg/
Never trust an operating system you don't have sources for. ;-)