Solving the ext3 latency problem
Posted Apr 20, 2009 0:29 UTC (Mon) by tytso
In reply to: Solving the ext3 latency problem
Parent article: Solving the ext3 latency problem
Unless there is a significant performance penalty by updating metadata only after the data has been written, instead of having another mode, this is probably how writeback mode should work.
(Note that data=guarded is only deferring the update of i_size, and not any other form of metadata.)
We'll have to benchmark it and see. It does mean that i_size gets updated more, and so that means that the inode has to get updated as blocks are staged out to disk, so that means some extra writes to the journal and inode table. I don't think it should be noticeable, at least for most workloads, since it should be lost in the noise of the data block I/O, but it is extra seeks and extra writes.
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