[Samba] dbench strange results

Piotr Legiecki piotrlg at pum.edu.pl
Mon Aug 1 06:15:10 MDT 2011


Hi

I'm building new samba server (on Debian 6.0, software RAID10 2TB, Xeon 
CPU). Generally everything is working fine, so I have decided to run 
some stress tests. My choice was dbench. Old server is Debian 4.0 (samba 
3.0.24, Athlon 3000+, one ATA 160GB disk). So run
dbench 16
on both old and new server

The results are strange

old serwer: about 300MB/sek (dbench 3.0)
and below are first seconds of dbench output

>   16      1766   398.71 MB/sec  warmup   1 sec
>   16      4852   334.46 MB/sec  warmup   2 sec
>   16      7956   317.26 MB/sec  warmup   3 sec
>   16     11117   309.62 MB/sec  warmup   4 sec
>   16     14357   298.27 MB/sec  warmup   5 sec
>   16     17579   295.52 MB/sec  warmup   6 sec
>   16     20912   294.48 MB/sec  warmup   7 sec
>   16     24167   292.58 MB/sec  warmup   8 sec
......

new server: about 80MB/sek (dbench 4.0)
and below are first seconds of dbench output

>   16       859   347.35 MB/sec  warmup   1 sec  latency 420.932 ms
>   16      1535   203.14 MB/sec  warmup   2 sec  latency 625.747 ms
>   16      2905   175.82 MB/sec  warmup   3 sec  latency 466.965 ms
>   16      3705   147.27 MB/sec  warmup   4 sec  latency 511.865 ms
>   16      5111   142.35 MB/sec  warmup   5 sec  latency 543.783 ms
>   16      5961   130.80 MB/sec  warmup   6 sec  latency 830.662 ms
>   16      7413   130.37 MB/sec  warmup   7 sec  latency 875.614 ms
>   16      8235   122.21 MB/sec  warmup   8 sec  latency 450.523 ms
>   16      8448   110.87 MB/sec  warmup   9 sec  latency 743.648 ms
>   16      9725   110.55 MB/sec  warmup  10 sec  latency 841.132 ms
>   16     10901   110.39 MB/sec  warmup  11 sec  latency 291.013 ms
>   16     12014   109.05 MB/sec  warmup  12 sec  latency 537.937 ms
......

Please nore that on old server MB/sec are rather constant (about 300MB/s 
) but on new one are dropping rapidly (at the end to about 80MB/s).

So what is going on? the new server is really fast (tested with iozone).

Regards
P.


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