[dm-devel] direct-io regression [Was: How to track down abysmal performance ata - raid1 - crypto - vg/lv - xfs]

[Chris Mason]

On Thu, Aug 05, 2010 at 02:58:37PM -0400, Jeff Moyer wrote:
> Chris Mason <chris.mason at oracle.com> writes:
> 
> > But, I'm surprised your drive is doing 8K dio reads at 16MB/s, that
> > seems a little high.  
> 
> I'm not sure why you think that.  We're talking about a plain old SATA
> disk, right?  I can get 40-50MB/s on my systems for 8KB O_DIRECT reads.
> What am I missing?

Clearly I'm wrong, his drive is going much faster ;)  I expect the
smaller reads to be slower but the drive's internal cache is doing well.

-chris