* Holger Kiehl (Holger.Kiehl@dwd.de) wrote:

There is however one difference, here I had set
/sys/block/sd?/queue/nr_requests to 4096.

Well from that it looks like none of the queues get about 255
(hmm that's a round number....)

avg-cpu:  %user   %nice    %sys %iowait   %idle
           0.10    0.00   21.85   58.55   19.50

Fair amount of system time.

Device:    rrqm/s wrqm/s   r/s   w/s  rsec/s  wsec/s    rkB/s    wkB/s 
avgrq-sz avgqu-sz   await  svctm  %util

sdf        11314.90   0.00 365.10  0.00 93440.00    0.00 46720.00     0.00  
255.93     1.92    5.26   2.74  99.98
sdg        7973.20   0.00 257.20  0.00 65843.20    0.00 32921.60     0.00   
256.00     1.94    7.53   3.89 100.01

There seems to be quite a spread of read performance accross the drives
(pretty consistent accross the run); what makes sdg so much slower than
sdf (which seems to be the slowest and fastest drives respectively).
I guess if everyone was running at sdf's speed you would be pretty happy.

If you physically swap f and g does the performance follow the drive
or the letter?

Dave
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