Mikael Abrahamsson wrote:

On Wed, 30 Jun 2010, Roman Mamedov wrote:

quoted

This is not necessary. See the dd man page about the conv=fdatasync 
switch.
You can even test with just 256 MB this way, and still get an extremely
accurate result.

You're right, for writing this is ok. For read tests it's important to 
use more than ram though, to avoid doing performance testing from 
block cache instead of from the actual drives.

See /proc/sys/vm/drop_caches.

-- 
Bill Davidsen [off-list ref]
  "We can't solve today's problems by using the same thinking we
   used in creating them." - Einstein