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. 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
• IOMeter: Multithreaded Write

When there is one thread of read requests, the standings are the same as in the sequential read test. The picture changes dramatically when we add a second thread, though. Every HDD suffers a performance hit: the drives from Western Digital and Hitachi slow down by a third whereas the others, by half and more. The HDDs from Toshiba and Seagate are the slowest in this test. Like many other drives from Seagate, this model is about ten times slower when reading two threads, providing an indecently low speed.

The HDDs slow down some more when we add a third and fourth thread. The overall picture remains the same as at two threads except that the Fujitsu does not lose its speed as quickly as the others and joins the group of leaders as the consequence. The 320GB model from Western Digital is the best among the leaders, enjoying a large lead over the closest pursuer when reading multiple data threads.

It’s different at writing. The drives do not slow down that much when switching from one to two threads, and the standings are somewhat different, too. The Seagate is a clear winner with two write threads. The Samsung and Fujitsu keep up a high enough speed when processing two threads. The two drives from Toshiba and the Hitachi are slower than others.

When we add more data threads, the drives split up into three groups. The Seagate and the 320GB Western Digital are in the lead, followed by the Fujitsu, Samsung and 250GB Western Digital. The drives from Toshiba and Hitachi are in the slow group.