Multithreaded Read & Write Patterns

The multithreaded tests simulate a situation when there are one to four clients accessing the virtual disk at the same time – the clients’ address zones do not overlap and the number of outstanding requests from each client varies from 1 to 8. We will discuss diagrams for a request queue of 1 as the most illustrative ones. When the queue is 2 or more requests long, the speed doesn’t depend much on the number of applications. You can also click the following links for the full results:

• IOMeter: Multithreaded Read
• IOMeter: Multithreaded Write

Well, each drive is quite sensitive to the number of read threads. Western Digital’s products are better than others but the 500GB model slows down suddenly when processing four threads. The Hitachi behaves in the same manner but its performance hit at four threads is terrible – it has only one tenth of its single-thread speed then. The Samsung, on the contrary, slows down at two threads but then does not change much at three or four threads.

The HDDs have the same amount of cache memory and should not differ much in terms of caching and writing. However, Western Digital’s products are good (note that there is about the same gap between them at every load). The Samsung copes very well, being ahead of the 500GB Western Digital with multiple threads. Having showed an excellent deferred writing in previous tests, the Hitachi is unexpectedly the worst drive when writing multiple threads simultaneously.