gmirror

[Paul Mather]

On Sat, 2005-05-14 at 11:30 +0100, Dominic Marks wrote:

> The seek times are way down, which is great, and makes sense using a
> round-robin strategy on the mirror, but my peak transfer rate has been
> almost halved too.
> 
> I don't mind this too much as in my application low seek times are worth
> more than high transfer rates, but it is still puzzling to me to see such a
> remarkable drop in throughput.

For large sequential reads on a round-robin mirror, you might be forcing
each drive to do a lot more small seeks than if you just accessed the
data from a single drive, and those small seeks may be slowing down the
overall transfer significantly.  I would have thought that large,
whole-track caches prevalent on modern hard disks would ameliorate that
problem in an otherwise quiescent environment, but, dependent upon the
drive's caching policy, you never know...

Cheers,

Paul.
-- 
e-mail: paul at gromit.dlib.vt.edu

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