Re: troubleshooting I/O performance bottleneck

[Thor Lancelot Simon <tls%rek.tjls.com@localhost>]

On Tue, Apr 28, 2009 at 01:26:01PM +0200, Manuel Bouyer wrote:
> 
> This is also what I get on my test box. iostat -x shows that the vnd0
> device is getting write requests of 32k (this is expected as the
> xbd interface can't do 64k transfers so MAXPHYS is set to 32k for domUs),
> and writes are forwarded to the disk as a stream of 32k requests.
> When the write is done from dom0 the disk gets a stream of 64k requests.
> This would explain the slowdown.

Why isn't xbdback already aggregating these requests?

Thor