[NCLUG] Backup idea

[Sean Reifschneider]

On Thu, Oct 11, 2007 at 01:34:07PM -0600, Bob Proulx wrote:
>Hmm...  This sounds very much like 'pdumpfs'.  Is that what you are
>using?  I have been using it for a while and it works pretty well.
>
>  http://0xcc.net/pdumpfs/index.html.en

I'd guess it's an implementation of the fairly common recipe of doing an
rsync and then "cp -al" of that directory to one named for the current
date.  Pretty common...

The down side is that it takes quite a lot of time to remove the daily
snapshots, and large files that change a bit regularly consume vast amounts
of memory.  A 2GB log file that gets small additions every day will grow by
another 2GB daily...

>> does it get unmounted and removed, or does the whole volume group go
>> into a state of stuck?
>
>I think it acts like a full filesystem.  It would be useful to test
>this assumption before relying upon it for backup.  I have a vague

The snapshot volume has to have enough space to hold copies of all blocks
on the original file system that are changed.  In the past if your snapshot
volume ran out of space, you were out of luck.

Try using rdiffbackup.

If, if you're up for an adventure, ZFS has great snapshot support.  The
nice thing about snapshots is that you can do "rsync --inplace".  This
doesn't suffer from the large-file-growing issue.  ZFS also has compression
built in.

Sean
-- 
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Sean Reifschneider, Member of Technical Staff <jafo at tummy.com>
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