On Mon, Sep 04, 2017 at 12:31:54PM +0300, Marat Khalili wrote: > Hello list, > good time of the day, > > More than once I see mentioned in this list that autodefrag option > solves problems with no apparent drawbacks, but it's not the > default. Can you recommend to just switch it on indiscriminately on > all installations? > > I'm currently on kernel 4.4, can switch to 4.10 if necessary (it's > Ubuntu that gives us this strange choice, no idea why it's not 4.9). > Only spinning rust here, no SSDs.
autodefrag effectively works by taking a small region around every write or cluster of writes and making that into a stand-alone extent. This has two consequences: - You end up duplicating more data than is strictly necessary. This is, IIRC, something like 128 KiB for a write. - There's an I/O overhead for enabling autodefrag, because it's increasing the amount of data written. Hugo. -- Hugo Mills | The future isn't what it used to be. hugo@... carfax.org.uk | http://carfax.org.uk/ | PGP: E2AB1DE4 |
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