Which file system automatically computes and stores hashes of files and later checks them at access to detect corruption?
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Sounds like a homework question. Especially the way it's asked. – Travis Aug 03 '09 at 20:22
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7during the summer vacations? – Adrian Panasiuk Aug 03 '09 at 20:34
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1Good point! :-) But I could just imagine this question with a **5)** in front of it on a printed piece of paper. – Travis Aug 05 '09 at 19:32
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@AdrianPanasiuk Now wait for someone to come and say "Sounds like someone who failed exams and got homework for summer" :D – AnonymousLurker Aug 05 '12 at 18:37
1 Answers
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Sun's ZFS does:
With ZFS, all data and metadata is checksummed using a user-selectable algorithm. Traditional file systems that do provide checksumming have performed it on a per-block basis, out of necessity due to the volume management layer and traditional file system design. The traditional design means that certain failure modes, such as writing a complete block to an incorrect location, can result in properly checksummed data that is actually incorrect. ZFS checksums are stored in a way such that these failure modes are detected and can be recovered from gracefully. All checksumming and data recovery is done at the file system layer, and is transparent to applications.
And so does Linux's btrfs: Btrfs also supports both data and metadata checksumming. Data checksumming is optional and can be disabled by mounting with -o nodatasum.
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Further, if your filesystem is mirrored, I believe it can recover from the error. – Mechanical snail Oct 15 '11 at 23:16