Messages in this thread | | | Date | Fri, 3 Nov 2006 02:34:28 +0100 (CET) | From | Mikulas Patocka <> | Subject | Re: New filesystem for Linux |
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>> There was discussion about it here some times ago, and I think the result >> was that the IDE bus is reset prior to capacitors discharge and total loss >> of power and disk has enough time to finish a sector --- but if you have >> crap power supply (doesn't signal power loss), crap motherboard (doesn't >> reset bus) or crap disk (doesn't respond to reset), it can fail. > > Hmm, maybe. But I think I saw couple of such bad sectors that were only bad > because of power loss in the wild. > > >> BTW. reiserfs and xfs depend on this feature too. ext3 is the only one that >> doesn't. > > Well, at least for XFS everybody tell that it should be used with UPS only if > you really care about your data. I think it has something to do with heavy > in-RAM caching this filesystem does.
System is allowed to cache anything unless sync/fsync is called. Someone told that XFS has some bugs that if crashed incorrectly, it can lose already synced data ... don't know. Plus it has that infamous feature (not a bug) that it commits size-increase but not data and you see zero-filed files.
> Anyway, it looks strange to list something very fragile and potentially not > existing in the requirements... :-)
Better to list it than quitly depend on it like ext2/fat/reiser/xfs/ (maybe jfs?) do.
> Could you explain where exactly do you depend on this requirement? And what > could happen if it is not true?
If you write a file in a directory and the sector is unwritable upon write & crash, you lose those few files near it. Just the similar way you would lose 4 files in inode table on ext2 in this case.
> Thanks, > > Grzegorz Kulewski > > > PS. Do you have any benchmarks of your filesystem? Did you do any longer > automated tests to prove it is not going to loose data to easily?
I have, I may find them and post them. (but the university wants me to post them to some conference, so I should keep them secret :-/)
Mikulas
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