Tagged queueing = lower write throughput?

[Albert Max Lai]

On Thursday, 2 September 1999, P.C. Uiterlinden wrote:

> While playing with RAID0, I found out that enabling tagged queueing
> deteriorates write throughput considerably. The MD driver seems not

I have noticed that one has to play around with the queueing depth to
get the highest throughput. With my IBM DGVSO9U (9ZX), the optimal
queuing depth is between 12-14. With my Quantum Viking 4.5 NSE, having
tagged queueing turned on slows it down.

> the one to blame: with a single disk it also happens. I did not
> expect this behavior nor can I explain it. What I would expect was
> a slight improvement (especially with multiple processes), but
> certainly not a rather big deterioration! I hope someone can explain
> this. Any help would be highly appreciated.

-- 
Albert Lai <amlai at columbia.edu>
http://www.columbia.edu/~aml61


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