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Re: RAID gotchas!



Justin W wrote:

> I'm currently in the process of rewriting the script and such so that
> there is not so much manual input.  If I succeed, the script should be
> quite portable across similar setups, but for now, you're going to have
> to change many of the path names to how they apply to you.

Your approach is interesting, because (in likely conditions) you use
the fastest method to create the first copy (dd) and the fastest
method to update the backup (rsync). Then, you keep two options
for restoration: total fileystem (dd) and selective file copy.

The only tricky part I see is what happens when you enlarge
your filesystem (which I suppose you sometimes do, as you use LVM).

You have to recreate the image with dd; otherwise you have to
manually extend the image file and the filesystem contained in it.
This is possible but you have to calculate the new size very
accurately; you managed to avoid that when creating the first copy
as dd handled the end of partition for you.
It could be automated with something like
  lvs -o lv_size --units=b --nosuffix --noheadings vgname/lvname

Thinking about it, the extension of the file image can be done
very quickly using dd seek=xxx (obtaining a sparse file).

Best regards.
-- 
   Roberto Ragusa    mail at robertoragusa.it


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