[systemd-devel] [ANNOUNCE] systemd 219

[Lennart Poettering]

On Wed, 18.02.15 12:13, Joonas Sarajärvi (muep at iki.fi) wrote:

> 2015-02-18 12:07 GMT+02:00 Lennart Poettering <lennart at poettering.net>:
> > On Wed, 18.02.15 06:22, Andrei Borzenkov (arvidjaar at gmail.com) wrote:
> 
> >>
> >> btrfs checksumming theoretically allows you to transparently recover
> >> after media corruption if filesystem has redundancy (more than one copy
> >> of data). Journald checksum will probably detect corruption, but can it
> >> repair it?
> >
> > No it cannot.
> >
> > But btrfs checksumming cannot fix things for you either if you lose
> > non-trivial amounts of data. It might be able to fix a few bits of
> > errors, but not non-trivial amounts. I mean, that's a simple property
> > of error correction codes: the more you want to be able to correct the
> > longer must your checksum be. Neither btrfs' nor journald's are
> > substantial enough to correct even a sector...
> >
> > Lennart
> >
> 
> My impression is that btrfs can fix the corruption in cases where a
> e.g. a RAID1 of btrfs is used. 

FS_NOCOW does no effect btrfs raid settings. If you want this kind of
data redundancy then it will continue to be available even though we
set FS_NOCOW now.

Lennart

-- 
Lennart Poettering, Red Hat