On Jan 9, 2008, at 9:09 PM, Rob Logan wrote:
>
> fun example that shows NCQ lowers wait and %w, but doesn't have
> much impact on final speed. [scrubbing, devs reordered for clarity]
Here are the results i found when comparing random reads vs.
sequential reads for NCQ:
http://blogs.sun.com/eri
On 10 January, 2008 - Rob Logan sent me these 1,9K bytes:
>
> fun example that shows NCQ lowers wait and %w, but doesn't have
> much impact on final speed. [scrubbing, devs reordered for clarity]
The final speed is limited by the slowest of your two raidz groups, so a
better example would be two
fun example that shows NCQ lowers wait and %w, but doesn't have
much impact on final speed. [scrubbing, devs reordered for clarity]
extended device statistics
devicer/sw/s kr/skw/s wait actv svc_t %w %b
sd2 454.70.0 47168.00.0 0.0 5.7 12.6
I've been looking into the performance impact of NCQ. Here's what i
found out:
http://blogs.sun.com/erickustarz/entry/ncq_performance_analysis
Curiously, there's not too much performance data on NCQ available via
a google search ...
enjoy,
eric
