Re: Hard link / rsync backup strategy successful

I'm in agreement. That is a recipe for a failed recovery.

If you must use some file system / volume trickery to get an initial backup
then I would suggest looking into LVM or some similar volume manager. For
beginners, take a look at the link below.

http://tldp.org/HOWTO/LVM-HOWTO/snapshots_backup.html

The technique does work however if you're using the PostgreSQL PITR backup
method, which is what I am guessing at, then you're only adding overhead and
complexity to the process.

Greg

On Tue, Jul 14, 2009 at 3:03 PM, Chander Ganesan <chander(at)otg-nc(dot)com> wrote:

> Kevin,
>
> Kevin Grittner wrote:
>
>> As a follow-up to this:
>> http://archives.postgresql.org/pgsql-admin/2009-03/msg00233.php
>>
>>
> I just read this post. What exactly does doing the hard link buy you here?
> Since it's just another inode pointer to the same file, I fail to see what
> the purpose of it is... For example, take a look at the code below :
>
> chander(at)bender:~$ echo "apple" > a
> chander(at)bender:~$ cat a
> apple
> chander(at)bender:~$ cp -l a b
> chander(at)bender:~$ cat b
> apple
> chander(at)bender:~$ echo "pear" > a
> chander(at)bender:~$ cat b
> pear
>
> Just curious... It seems that the method described in your email (creating
> a backup using 'cp -l' and then using rsync) would "break" your old backup
> (the hard link copy) since some of the files in it would be modified, but it
> would be missing the "new" files that were added to the backup. Essentially
> making your "old" backup an incomplete backup of your new cluster.
>
> In essence, a "hard link" isn't a copy of any sort, it's just a pointer to
> the same inode, which is the exact same data...
>
> Perhaps there is something that I am missing here?
>
> Thanks
>
> --
> Chander Ganesan
> Open Technology Group, Inc.
> One Copley Parkway, Suite 210
> Morrisville, NC 27560
> 919-463-0999/877-258-8987
> http://www.otg-nc.com
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