Re: overlay file to test btrfs repairs

[Duncan <1i5t5.duncan@cox.net>]

Chris Murphy posted on Sun, 20 Mar 2016 21:43:52 -0600 as excerpted:

> Hi folks,
> 
> So I just ran into this:
> https://raid.wiki.kernel.org/index.php/
Recovering_a_failed_software_RAID#Making_the_harddisks_read-
only_using_an_overlay_file

[That's a single link, wrapped by my client.]
 
> This is a device mapper overlay file - not overlayfs.
> 
> For the repairs that are sometimes uncertain what's next, maybe this is
> a viable option to avoid changing the file system? I'm thinking
> chunk-recover might take up too much space, I'm not sure how that one
> works, if chunks are just being read or if they have to be rewritten or
> if it's just the chunk tree? But for 'btrfs check' and 'btrfs rescue
> super-recover/zero-log' there should be very little being written so the
> overlay idea might be a good step?
> 
> Opinions?

That's a creative and potentially quite useful possible solution to an 
often hairy problem.  Thanks for bringing it up. =:^)

Provided Hugo and the devs don't find major fault with the idea, linking 
that from appropriate locations (as a possible solution in the Problem 
FAQ is the first one that occurs to me) in the btrfs wiki could be quite 
useful, to many.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman