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chunkfschunkfsPosted Apr 27, 2007 8:05 UTC (Fri) by dlang (✭ supporter ✭, #313)In reply to: chunkfs by pimlott Parent article: Filesystems: chunkfs and reiser4
sorry for the sloppy typing, I was in too much of a hurry to finish the post
yes, the time to fsck 100x10Gb filesystems is expected to be significantly less then to fsck 1x1TB filesystem
in part this is also a memory limited operation, when doing the fsck you need to remember all the files that you have seen to see if any of the others overlap it. besides reducing n during the O(n^2) portion by 100x (even though you have to do it 100 times) you also drasticly reduce the amount of ram needed, avoiding swap or other low-memory conditions
yes, you do need to do a fsch from time to time, but under a crash condition you may be able to skip doing one for the chunks that have not been changed and so are still marked clean. and yes, people do still use non-journaling filesystems. when you journal you end up doing lots of writes twice (and a lot of seeking between the journal write and the final write). if you have lots of extra disk bandwidth you may be able to afford to do this, but if you don't have the extra disk bandwidth your entire system will slow down while the journal is flushed. for some applications (data capture for example) this isn't acceptable
in addition, you can do a check of a few chunks every boot rather then doing a check of everything every 30 boots (spreading the maintinance pain over time rather then having it hit in one massive chunk)
did I do a better job of explaining it this time?
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