Re: kernel version impact on PostgreSQL performance

Greg Smith wrote:
> 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.4030909@2nd
> quadrant.com
>
> 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.

Maybe that question is dumb, but why should a change in ext4 have an
impact on a figure that was generated with ext3? To quote the link:

"the PostgreSQL performance atop the EXT3 file-system has fallen off a cliff"

Yours,
Laurenz Albe