Re: Backup media; comments would be appreciated.

From: Nico Kadel-Garcia (nkadel_at_comcast.net)
Date: 01/12/04


Date: Sun, 11 Jan 2004 23:55:28 -0500


"Travis Casey" <efindel@earthlink.net> wrote in message
news:of4ttb.vcr.ln@lostthoughts.org...
> Nico Kadel-Garcia wrote:
> > "Richard Steven Hack" <richardhack@prontomail.com> wrote:
>
> >> Well, relatively speaking, if you have a hard disk which is not too
> >> old, the odds of it failing are FAR lower than the odds of a bad read
> >> on a CD or tape.
> >>
> >> Of course, if the building containing it burns down, it's toast, but
> >> I'm talking about media problems here. Hard disks simply do not have
> >> the same level of problems that CD and tape do.
> >
> > But they're expensive, and vulnerable to types of catastrophic failure
> > (such as "rm -rf /") that your tapes are pretty immune from.
> >
> > Now, I don't know if there's a cheap way to do what NetApps do: They
> > provide a sort of ".backup/hourly", ".backup/daily", or ".backup/weekly"
> > backup where your files are synced off to a read-only sort of
file-system
> > and those files protected from user editing, but they don't take up a
heck
> > of a lot of file space because they're hard-linked together.
> >
> > It's fairly neat: I've never tried to do it on a Linux file system, and
I
> > don't know if you can do it with your boot OS, but it's really useful
for
> > NFS servers.
>
> Yes, there's a cheap way to do that; in fact, that's what the link I
posted
> a few weeks back tells how to do, using rsync, and hard-linking files as
> you mention.
>
> http://www.mikerubel.org/computers/rsync_snapshots/
>
> I currently run a nightly backup of my two home machines, with each
backing
> up to the other, using the methods outlined there. It keeps seven days of
> daily backups and four weeks of weekly. If I wanted to, I could make it
> back up every hour, and/or keep backups around longer.
>
> And, of course, this isn't vulnerable to an "rm -rf /", since the backup
is
> on another machine, and is not mounted.

Yeah, that onen I know. But what I meant was more like this: I'm logged onto
an NFS client of a NetApp, in /home/nkakdel. I do an "ls -a" and get this.

.bashrc
.emacs.el
mbox
project-directory

I now do "ls -l .backup" and see this.

hourly
daily
weekly
monthly

I now do an "ls -l .backup/daily" and see this.

.bashrc
.emacs.el
mbox
mbox~
project-directory

And if I look in that .backup/daily/project directory, I see the files as
they were last night, and I deleted that mbox~ file this morning, so this is
right.

Merging multiple rsync repositories to reduce the disk space taken is
non-trivial: NetApps seem to do some clever things right in the kernel and
file system to prevent having to duplicate entire, unchanged filesystems
into the backup system.



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