Re: Citation Needed: BTRFS Failure Resistance

[Hugo Mills <hugo@carfax.org.uk>]

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On Wed, May 22, 2019 at 09:46:42PM +0300, Cerem Cem ASLAN wrote:
> Could you confirm or disclaim the following explanation:
> https://unix.stackexchange.com/a/520063/65781

   Well, the quoted comment at the top is accurate (although I haven't
looked for the IRC conversation in question).

   However, there are some inaccuracies in the detailed comment
below. These aren't particularly relevant to the argument addressing
your question, but do detract somewhat from the authority of the
answer. :)

   Specifically: Btrfs doesn't use Merkle trees. It uses CoW-friendly
B-trees -- there's no csum of tree contents. It also doesn't make a
complete copy of the tree (that would take a long time). Instead,
it'll only update the blocks in the tree that need updating, which
will bubble the changes up through the tree node path to the top
level.

   There's a detailed description of the issues of broken hardware on
the btrfs wiki, here:

https://btrfs.wiki.kernel.org/index.php/FAQ#What_does_.22parent_transid_verify_failed.22_mean.3F

   Hugo.

-- 
Hugo Mills             | Why play all the notes, when you need only play the
hugo@... carfax.org.uk | most beautiful?
http://carfax.org.uk/  |
PGP: E2AB1DE4          |                                           Miles Davis

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