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From Brandon Williams <dri...@gmail.com>
Subject Re: Problems with Python Stress Test
Date Fri, 04 Feb 2011 01:22:51 GMT
On Thu, Feb 3, 2011 at 7:02 PM, Sameer Farooqui <cassandralabs@gmail.com>wrote:

> Hi guys,
>
> I was playing around with the stress.py test this week and noticed a few
> things.
>
> 1) Progress-interval does not always work correctly. I set it to 5 in the
> example below, but am instead getting varying intervals:
>

Generally indicates that the client machine is being overloaded in my
experience.

2) The key_rate and op_rate doesn't seem to be calculated correctly. Also,
> what is the difference between the interval_key_rate and the
> interval_op_rate? For example in the example above, the first row shows 6662
> keys inserted in 5 seconds and 6662 / 5 = 1332, which matches the
> interval_op_rate.
>

There should be no difference unless you're doing range slices, but IPC
timing makes them vary somewhat.

3) If I write x KB to Cassandra with py_stress, the used disk space doesn't
> grow by x after the test. In the example below I tried to write 500,000 keys
> * 32 bytes * 5 columns = 78,125 kilobytes of data to the database. When I
> checked the amount of disk space used after the test it actually grew by
> 2,684,920 - 2,515,864 = 169,056 kilobytes. Is this because perhaps the
> commit log got duplicate copies of the data as the SSTables?
>

Commitlogs could be part of it, you're not factoring in the column names,
and then there's index and bloom filter overhead.

Use contrib/stress on 0.7 instead.

-Brandon

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