Date: Mon, 11 Oct 1999 12:44:37 -0700 From: Darryl Okahata <darrylo@sr.hp.com> To: freebsd-questions@FreeBSD.ORG Subject: Re: Why use tape for backups? (was: backup method reccommendation?) Message-ID: <199910111944.MAA11982@mina.sr.hp.com> In-Reply-To: Your message of "Mon, 11 Oct 1999 09:47:48 EDT."
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FreeBSD Bob <fbsdbob@weedcon1.cropsci.ncsu.edu> wrote:
> What are the pros and cons of doing backups on CD's?
* Small capacity. Even with compression, CD's don't hold much. Of
course, if you don't have a lot to back up, this isn't an issue.
However, if the data won't fit onto a single CD, plan on babysitting
the computer and feeding it disks.
* Speed is "decent", but not great (however, it can be great if you take
price into account). Unless you have a recent-generation CDR/CDRW,
the write speed is, at most, 4X, which is 600KB/sec. It's probably
even worse with CDRW, as many drives seem to write CDRW media at a
slower speed than CDR. Still, many inexpensive tape drives transfer
data at well under 1MB/sec (early DAT drives, for example, transfer
data at 150KB/sec), and so CD's aren't that bad.
* Multi-disk backups are problematic. Unless you write your own backup
software, I think you have to use split(1) to slice'n dice the output
from dump/tar, and then write the resulting files to CDs. You
basically need lots of free disk space, to use as a staging area.
* If you're environmentally conscious, writing backups to CDRs (as
opposed to CDRWs) is environmentally hostile. ;-)
> I have been doing archiving on CD's for some months, and that seems
> to be working, but, it is a real hassle to go through the motions of
> tarring/compressing/isoing to write to a cd.... more than should be
> necessary.
Except for "feeding disks to the drive", it's straightforward to
write scripts to automate this, as long as you have enough free disk
space to use as a staging area.
> Are there any good ways to use CD's as ``quasi tape devices'' rather
> than mountable devices? Something like dumping to a file, then
> dding the file directly to the CDdevice is what I would like to do.
> Then if a recovery is needed, restore directly from the CD, like tape.
What's wrong with mounting? It's easy to do. You can make a
bootable FreeBSD floppy with the CDROM driver on it (I think the fixit
floppy already has it). In that case, you can just store the backup as
a file on the CDROM. When you need to restore, you boot from the
floppy, mount the CDROM, and restore. No muss, no fuss.
--
Darryl Okahata
darrylo@sr.hp.com
DISCLAIMER: this message is the author's personal opinion and does not
constitute the support, opinion, or policy of Hewlett-Packard, or of the
little green men that have been following him all day.
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