Re: RedHat 7.4 Release Notes: "Btrfs has been deprecated" - wut?

[Christoph Anton Mitterer <calestyo@scientia.net>]

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On Mon, 2017-08-14 at 14:36 +0800, Qu Wenruo wrote:
> > And how are you going to write your data and checksum atomically
> > when
> > doing in-place updates?
> 
> Exactly, that's the main reason I can figure out why btrfs disables 
> checksum for nodatacow.

Still, I don't get the problem here...

Yes it cannot be done atomically (without workarounds like a journal or
so), but this should be only an issue in case of a crash or similar.

And in this case nodatacow+nochecksum is anyway already bad, it's also
not atomic, so data may be completely garbage (e.g. half written)...
just that no one will ever notice.

The only problem that nodatacow + checksuming + nonatomic should give
is when the data was actually correctly written at a crash, but the
cheksum was not, in which case the bogus checksum would invalidate the
good data on next read.

Or do I miss something?


To me that sounds still much better than having no protection at all.


Cheers,
Chris.

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