HAMMER problems with ciss

[György Vilmos]

On 08/08/2009, Matthew Dillon <dillon at apollo.backplane.com> wrote:
>     It will depend on what kind of test you are running.  Anything
>     that calls fsync() is going to be fairly horrible for HAMMER...
>     flushing the filesystem is very expensive and going to remain
>     that way for a while.
>
>     Normal sequential write I/O without fsync() should be fairly close
>     to platter rates, at least that is what I get, e.g. with something
>     like dd.
Sysbench, and yes, it calls fsync. I get about half of the UFS performance data.
dd is OK.

The performance is also lower when reading, here are some lines from
the random read test:
dfly hammer:
#bklsize[kB]    MBps    iops    min     avg     max     95%     -
latency times in ms
1               .14     150.77  0.0000  0.0066  2.4605  0.0101
2               .34     177.72  0.0000  0.0056  1.5467  0.0083
4               .64     165.02  0.0000  0.0060  2.7946  0.0087
8               1.39    179.03  0.0000  0.0056  0.0179  0.0084
16              2.59    166.17  0.0000  0.0060  4.1047  0.0086
32              4.81    153.94  0.0000  0.0065  0.8895  0.0103
64              10.59   169.49  0.0000  0.0059  2.5563  0.0085
128             15.54   124.35  0.0001  0.0080  3.3134  0.0117
256             29.90   119.61  0.0001  0.0083  2.2407  0.0116

fbsd8 UFS:
#bklsize[kB]    MBps    iops    min     avg     max     95%     -
latency times in ms
1               .20     212.32  0.01    4.71    833.94  7.62
2               .40     206.95  0.01    4.83    321.63  7.84
4               .84     216.99  0.01    4.60    1751.44 7.47
8               1.65    211.71  0.01    4.72    321.55  7.66
16              3.34    214.37  0.01    4.66    245.09  7.54
32              6.34    203.13  0.01    4.92    570.37  7.88
64              11.66   186.58  0.02    5.36    516.09  8.40
128             20.30   162.41  0.04    6.15    517.97  9.41
256             34.13   136.54  0.07    7.32    667.05  10.74

This is with a P400, 512 MiB BBWC and a 15k RPM SAS disk.

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