Problem with writes on HD with FreeBSD 7

[Julien Drouard]

Hi,

Since a few weeks some of our database servers are running under FreeBSD 7 and we have noticed that writes on HD take a lot of time. To confirm our impression we ran sysbench. The results are the following :


*         Under FreeBSD 7 :

Random write :
Operations performed:  0 Read, 10000 Write, 12800 Other = 22800 Total
Read 0b  Written 156.25Mb  Total transferred 156.25Mb  (1.6459Mb/sec)
  105.34 Requests/sec executed

Test execution summary:
    total time:                          94.9312s
    total number of events:              10000
    total time taken by event execution: 41.1071
    per-request statistics:
         min:                            0.0000s
         avg:                            0.0041s
         max:                            0.1653s
         approx.  95 percentile:         0.0251s


*         Under FreeBSD 6.2 :

random write
Operations performed:  0 Read, 10005 Write, 12673 Other = 22678 Total
Read 0b  Written 156.33Mb  Total transferred 156.33Mb  (10.505Mb/sec)
  672.32 Requests/sec executed

Test execution summary:
    total time:                          14.8814s
    total number of events:              10005
    total time taken by event execution: 112.2531
    per-request statistics:
         min:                            0.0000s
         avg:                            0.0112s
         max:                            0.9868s
         approx.  95 percentile:         0.0010s

The command used for sysbench is : sysbench --num-threads=16 --test=fileio --file-total-size=3G --file-test-mode=rndwr run

I have found absolutely nothing to explain that differences so if someone can help me to solve this problem I would be very grateful.

Kind Regards,

Julien



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