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Initially for the tests we chose Adaptec ThreadMark 2.0. The main drawback of this test is low information given out - only one average weighted resulting value. Besides, when testing new fast discs it started to raise doubts. At least, correlation with WinBench results nearly disappeared. So, I decided to follow the StorageReview and start using Intel IOMeter test. The Trial Version can be downloaded here.

I used the technique developed by StorageReview. You can find it also there (Operating Systems and Benchmarks - Part 4 ). I will give you a short description of the test and test technique.

The IOMeter, unlike WinBench which is based on real applications, is a completely synthetical test. It gives high flexibility and creates a lot of difficulties for the tester in adjusting. Additional problems arise due to the fact that you can test not only one disc on a uniprocessor machine, but also disc arrays in multiprocessor configurations and even a set of computers on a net.

The IOMeter works with so called "workers". Intel recommends to create one worker per processor, that's why consider that we have one worker. After that each worker tests target(s), which are either one unpartitioned physical disc, or one or several partitions on a disc. Then, each worker receives its access pattern (a set of parameters according to which this worker organizes an access to the target).

An access pattern contains the following variables:

• Transfer Request Size - a minimal data unit to which the test can apply.
• Percent Random/Sequential Distribution - percentage of random requests. The other are, therefore, sequential.
• Percent Read/Write Distribution - percentage of requests for reading. Another important variable which is not directly included into the access pattern - # of Outstanding I/Os - defines a number of simultaneous I/O requests for the given worker and, correspondingly, disc load.

So, setting parameters ad arbitrium we can get a wide range of incomparable results which have little practical sense. And there arises a question: how to set an access pattern in order it models disc operation in real conditions? Here, I used the technique developed by StorageReview.

So, there are three access patterns - File Server (the model is defined by Intel and comes with the IOMeter), Workstation and Database (defined by StorageReview). Below you can see a table of parameters for each pattern, taken from StorageReview (Operating Systems and Benchmarks - Part 5 ). There you can read why these patterns were chosen.

Now a few words on the # of Outstanding I/Os parameter. If you set it to 1, then with the 100% Percent Random/Sequential Distribution we in fact measure a random access time. Value 4 corresponds to a load of an elementary applications like Windows Calculator. According to StorageReview, in average on real applications this parameter takes 30-50. The value more than 100 corresponds to high disc load (e.g. in case of defragmentation). According to it they suggest to take the following 5 values for this parameter.

Besides, you can set time of test running (in Trial Version it is done manually, pressing STOP button) and rump-up time. I has taken time for running each of 15 tests (5 loading types for each of 3 access patterns) equal to 10 min, and rump-up delay - to 30 sec. The physical discs are tested (unpartitioned and unformatted).

Now comes the main thing - what we get in the end. The following results were included:

• Total I/Os Per Second - an average number of requests implemented per second. A request consists of positioning and read/write of the unit of the corresponding size.
• Total MBs Per Second - the same, but in other words. If the patterns are working with the units of the same size (Workstation and Database) - it's just multiplication of Total I/Os Per Second by unit's size.
• Average I/O Response Time - for linear loading (1 outstanding I/O) - it's again the same as Total I/Os Per Second (Total I/Os Per Second = 1000 milliseconds / Average I/O Response Time). With load increase the value rises but not arcwise. The result depends on optimization of drive firmware, bus and OS.
• CPU Effectiveness, or I/Os per % CPU Utilization.

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