Dan Pritts wrote:
On Fri, Mar 24, 2006 at 05:35:12PM +0100, Tomasz Chmielewski wrote:
Why are full backups needed at all with BackupPC?
According to documentation, "BackupPC's CGI interface ``fills-in''
incremental backups based on the last full backup, giving every backup a
``full'' appearance."
So, in theory, it should be enough to make just one full, initial
backup, and then only incremental backups.
You can do that but as things change on the backup client, you will end
up with larger and larger incremental backups, using more bandwidth on
the wire. Maybe an issue for you, maybe not.
This is why it wonders me.
So far I've been using my own scripts based on rsync.
Basically, what I did, was to create a "latest" dir, and then hardlink
each and every file from it, to a given day dir:
latest - 2006-03-25
- 2006-03-24
- 2006-03-23
etc.
This way I had the exact state of the machines which were backed up with
rsync at any given day.
I decided to use BackupPC, as it features compression (important, as
there is no compressed filesystem for Linux), and pooling (less
important, but why not).
I have read on this list that when you use rsync, your "full" backups
won't transfer everything over the wire, but rather will intelligently
make use of the previous full, so there's not a big loss to having a full.
Yes, just use --link-dest option when hardlinking.
one issue you might need to weigh is that each full means lots and
lots of hard links get created on your filesystem. this takes lots
of time since the disk heads have to seek all over the place.
On the other hand, incrementals won't do this.
No, it doesn't take that long, hardlinking one server (say 5 GB data) to
another directory will take only a few minutes.
there are other backup schemes that do the "always make a full" thing,
do a web search for "mike rubel rsync backup" to see one guy's web
page that uses a similar scheme. It lacks many of the nice surrounding
tools that backuppc gives you.
I'd rather want BackupPC to have it :)
--
Tomasz Chmielewski
http://wpkg.org
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