Articles: Storage

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As you see, the set of commands supported by the FC Test has expanded.

We added a few commands for automation of the test process (Save, Recycle, Reboot) to the existing commands like Create, Read and Copy. The Pause command was required to better the “convergence” of the test results. It serves to stop the test for a while after a system reboot, so that the operating system could load itself up completely. Of course, this process takes different time with different computers, and we measured it experimentally, by measuring the time interval between a FC Test reboot (the FC Test starts up automatically after a system restart in the batch mode) and the end of the OS’s accesses to the hard disk drive. And, of course, we doubled this time, just in case J.

The System command allows expanding the scope of the benchmark practically infinitely. We can wake up any external application using this command, thus enhancing the capabilities of the FC Test as our needs require. Right now, we use this command for formatting hard disks.

The Compress and Decompress commands allow testing the speed of compression/decompression of files. In fact, the process of compression/decompression itself is simulated – the processor doesn’t perform any calculations as our goal is in creating a certain load onto the disk subsystem.

So how does the load on the disk subsystem at archiving differ from the load at copying? – Asymmetry!

When we’re copying files, the hard disk writes and reads the same amount of data. But when we’re archiving, we write less data than we read (if the data have been really compressed). The ratio of the amount of the original data to the resulting amount is called the compression ratio.

We suppose that the performance of a hard disk drive may differ in “asymmetrical” modes from its performance in the copy tests. How big this difference is and why it occurs? We’ll discuss it later…

Right now, let me only say that the Decompress command allows simulating the decompression process. In other words, the hard disk will be reading one large file and writing many small files…

One of the most important commands – Comment – helps to read a report file, even after you’ve tested something a year ago. One of its useful qualities is in adding a “carriage return” sign to the CSV-file, resulting in the following formatting:

This is the result of testing a Secure Digital card – we measured speeds of writing and reading three file sets. One file was 100MB big, then 10 files were 10MB each, and lastly, we had 100 files, 1MB each.

In the test report, you can see a formatted table with results where each line contains the write and read speeds for each file set.

Thus, my dream about a test that would write reviews by itself, fully automatically, seems to be closer to reality. We only have to train the benchmark to draw diagrams.

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