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 request queue depth varying from 1 to 8. The clients’ address zones do not overlap. We’ll 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, part 1
• IOMeter: Multithreaded Read, part 2
• IOMeter: Multithreaded Write, part 1
• IOMeter: Multithreaded Write, part 2

There are no surprises at one thread: the results are the same as in the sequential read test, the 3-platter Seagate having top place.

It is very different at two threads: Western Digital’s drives occupy three top positions, enjoying a large lead over the others. The Caviar Green with 16MB buffer is second, which is a sensational result for a 5400rpm drive. The desktop Caviar Black is better at reading two threads than the enterprise RE3. It is also interesting that the WD Green with 32MB buffer is slower than every Green series drive with 16MB buffer, including 4-platter models. The Seagate SV35.3 outperforms the 4-platter 7200.11 series model and is almost as fast as the 3-platter one. It seems to be optimized for multithreaded reading.

Hitachi’s drives with 16MB buffer are slow at multithreaded reading but the E7K1000 delivers average performance.

Samsung’s HDDs are the losers of this test. Like Seagate’s 7200.10 series products, they show very poor performance. They need just a little to show normal speed: a queue depth of 2 requests at least (you can see this if you take a look at the tables with numbers). Samsung’s new firmware must have been unable to identify two threads and worked with them as with one random read thread. It is sad since the desktop Samsung F1 model (even without the suffix DT) with older firmware had been among the leaders of this test in our previous review.

It’s all roughly the same at three threads but the Seagate SV35.3 takes fourth place now. This drive is not totally hopeless after all.

WD’s Green drive with 3 platters and 16 megabytes of cache takes first place when processing four threads, ousting its Black mate. That’s a truly impressive result.

When writing one thread, the drives repeat the results of the sequential test. The 3-platter Seagate, WD RE3 and Hitachi 7K1000.B are in the lead. The 4-platter WD Caviar Green and the 5-platter Hitachi occupy last places.

The picture changes dramatically when a second thread is added. The Hitachi 7K1000.B manages to keep its high speed but is outperformed by the Hitachi E7K1000 and the enterprise model from Samsung. The WD Caviar Black is slow. It is slower than the enterprise RE3 as well as the two 3-platter 5400rpm models. Seagate’s products have last places in this test. They are no good at multithreaded writing.

When there are three write threads, Samsung’s HDDs take top places. Third place goes to the WD RE3 while the Hitachi E7K1000 is fourth. Seagate’s drives are the losers again.

There are more changes with the addition of a fourth thread but we have the same leading trio. The WD Caviar Black is fast now. The 3-platter Seagate shows average performance while the Hitachi 7K1000.B is among the losers.