Re: speed of COW directory copying: XFS 20x slower than ext3

[Junichi Uekawa <dancer@netfort.gr.jp>]

Hi,

> We just discovered, that mounting XFS partition with:
> 
> sudo mount -o nobarrier /dev/sda2 /mnt/p1
> 
> speeds things up on all machines. The reason is, that the option "-o
> barrier" was added by default to all kernels >= 2.6.17, so dakol has
> nobarrier, all the others have barrier. By mounting with nobarrier,
> the cp and rm times are 5s on the first run and around 1.7s on
> subsequent runs. That's much better for XFS.


This is very interesting.

I have so far only tested cowdancer with ext3. Profiling and
optimizing code is done only for ext3.

I'm not quite sure how widespread other filesystems are, but it would
be interesting to see how they can be optimized better wrt cowdancer
usage.


regards,
	junichi
-- 
dancer@{debian.org,netfort.gr.jp}   Debian Project