Cyril Scetbon wrote:
Does anyone know what can be the differences between linux kernels 2.6.29 and 2.6.30 that can cause this big difference (TPS x 7 !)
http://www.phoronix.com/scan.php?page=article&item=linux_2624_2633&num=2

Discussed in detail at http://archives.postgresql.org/message-id/4b512d0d.4030...@2ndquadrant.com

You might need the background information at http://developer.postgresql.org/pgdocs/postgres/wal-reliability.html to be able to follow what that's talking about.

The short version is that ext3 combined with regular hard drives has never been safe for database use by default, it was cheating on writes in a way that left it possible for corruption to occur after a crash. The change in ext4 that caused the performance drop is from the kernel developers finally eliminating the source for that cheat. The result should be reliable operation by default, which unfortunately happens to be much slower operation by default too.

--
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
g...@2ndquadrant.com   www.2ndQuadrant.us


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