Re: 10g System statistics - single and multi

Christo,

my test was very simple and crude. I did for example not repeat it several times to get averages. I am not familiar with iometer, I just use Oracle to give me the timings, since it is also Oracle which will gather the timing for the system statistics, so the ela values are microseconds for a single block (sequential) read. The values are actually averages for all single block reads. Likewise, the other ela values are averages over their respective occurences. I redid the test, clearing the buffer between different dfrmc settings (by offlining the tablespace) and also ran the entire test twice and then also ran it with the tablespace on an EMC CX700. The findings are still the same, the hogher the number of blocks read with one IO (as seen from Oracle), the longer it takes => mreadtm > sreadtm

EMC CX700:

dfmrc	count	elapsed (usec)
1	1985	  297.355
3	1	  300.000
8	241	  564.423
11	4	  747.000
16	120	  989.733
32	60	1,771.250
64	30	3,241.100
128	15	6,295.133


1	1985	  288.202
3	1	  291.000
8	241	  605.867
11	4	  733.750
16	120	  935.692
32	60	1,714.833
64	30	3,234.767
128	15	6,199.000

IBM ESS 700 (Shark):

dfmrc	count	elapsed (usec)
1	1965	   545.717
7	1	 1,130.000
8	241	 1,283.353
15	1	 2,417.000
16	123	 2,637.959
31	1	 4,478.000
32	59	 4,715.203
63	1	 8,088.000
64	29	 8,294.862
127	1	16,496.000
128	14	16,250.071


1	1967	   693.753
7	1	 1,126.000
8	241	 1,293.324
15	1	 2,815.000
16	123	 2,647.301
31	1	 4,401.000
32	59	 4,701.898
63	1	 8,111.000
64	29	 8,250.310
127	1	15,436.000
128	14	15,570.214

The tablespace on the shark is an LMT with a 4M uniform extent size and the table spans 4 extents. The tablespace on the cx700 is an LMT with a 32M uniform extent size. That explains the differences in the read patterns.

Christo Kutrovsky wrote:

> Wolfgang,
>
> These results have been produced with Windows (for convenience) on
> unpartitioned drives with iometer (www.iometer.org). No caching on OS
> side.
>
> Random read from my SAN
> Test type Responce time (ms)
> 512 read-1 0.874
> 512 read-2 0.173
> 512 read-4 0.130
> 8k read-1 0.457
> 8k read-2 0.149
> 8k read-4 0.228
> 32k read-1 0.422
> 32k read-2 0.388
> 32k read-4 0.762
> 256k read-1 2.165
> 256k read-2 2.672
> 256k read-4 5.185
>

I don't quite understand how to read this. what does, e.g., "8k read-1" mean as opposed to "8k read-4"?

-- 
Regards

Wolfgang Breitling
Centrex Consulting Corporation
www.centrexcc.com
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