Parallel rsync's for better Performance.

[Matt McCutchen]

On Wed, 2009-10-28 at 17:24 +0100, Matthias Schniedermeyer wrote:
> On 28.10.2009 10:35, Matt McCutchen wrote:
> > On Wed, 2009-10-28 at 10:01 +0100, Matthias Schniedermeyer wrote:
> > > Otherwise parallel rsyncs completly kill any performance you had because 
> > > normal HDDs will fall into a seek-storm, when more than 1 rsync works on 
> > > them.
> > 
> > Asynchronous I/O may solve that, on OSes that support it.
> 
> No. That's a fundamental problem with ANY rotating media device.

"Solve" may be an overstatement, but asynchronous I/O would at least
help significantly because one process could issue many I/O requests to
the same area of disk at once, and the disk scheduler could fulfill all
of those requests before seeking elsewhere.  Without asynchronous I/O,
after the scheduler fulfills one request, it is left to either seek or
wait for the process to issue another request.

-- 
Matt