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Basic question on Quest Benachmark factory software ?


#1

I am running a Oracle TPC-C test using Quest Benchmark factory software. I am using Oracle 11g R2 RAC database and the database is on an iSCSI storage.

I am monitoring the I/O on my storage and observing the I/O pattern as follows.

Read : 30 to 40%
Write : 70 to 60%

I was of the opinion that TPC-C load means it should simulate something like 70%Read/ 30% write I/O pattern. Can you please clarify ? This is a basic question, but my impression of TPC-C is something similar to OLTP. In OLTP, we have more reads than write. But I am seeing completely opposite to that !!!

Thanks,
Shashi


#2

Shashi,

If you are getting your data from the array then the ratio will be impacted by everything between the array and the user load in the stack - specifically the host memory. As I’m sure you know the IO profile to the array from the host changes dramatically as you increase and decrease the amount of memory available to the database. If the memory is sufficiently large you end up with quite a few page re-hits in memory so only the initial reads hit the disk.

John Moran