[dm-crypt] The future of disk encryption with LUKS2

Michael Kjörling michael at kjorling.se
Mon Feb 8 12:34:04 CET 2016


On 8 Feb 2016 01:25 +0100, from sven at whgl.uni-frankfurt.de (Sven Eschenberg):
> I always
> wondered how a HDD exactly behaves when power fails, while a sector
> is in transit. My best hope is, that the CRC at the end of the
> sector does not match and an error is returned on the next read?

That's the theory; if a sector write is interrupted half way through
(regardless of the reason), then the FEC data doesn't match the sector
payload data. In this case, the difference is very likely large enough
that the error cannot be corrected using the FEC data, so you get a
read error back instead.

_Unfortunately_, theory and practice don't always agree. I think it
was Google that did a study on storage errors not all that long ago,
and one conclusion was that silent read errors (where you do get data
back from the drive, but that data is not the same as was originally
written), while rare, happens with a high enough probability to
warrant consideration in large storage systems.

-- 
Michael Kjörling • https://michael.kjorling.semichael at kjorling.se
                 “People who think they know everything really annoy
                 those of us who know we don’t.” (Bjarne Stroustrup)


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