Multithreaded Read & Write Patterns
The multithreaded tests simulate a situation when there are one to four clients accessing the hard disk at the same time – the clients’ address zones do not overlap. 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, part 1
- IOMeter: Multithreaded Read, part 2
- IOMeter: Multithreaded Write, part 1
- IOMeter: Multithreaded Write, part 2
There is only one drive that survives the addition of a second read thread without slowing down too much. This is the WD Blue A7. Interestingly, the WD Black series drive, which has been similar to the A7 throughout the previous tests, performs differently here, its performance plummeting more than twofold. There are HDDs, namely Seagate 7200.12, Seagate LP and WD Blue V1, that find it even harder, though. The Samsung F2 is especially poor. Showing the typical behavior of that generation of Samsung drives, it is as slow as 5 MBps.
When we add more read threads, we don’t see any big changes. There are but a few drives that deliver acceptable multithreaded read performance. These are the WD Blue A7 and M9, the WD Green with 16MB cache, and the Seagate 7200.11 (interestingly, these are mostly two-platter models, with only one exception).
Take note of the performance hit the Samsung F3 suffers at four threads. This new series does better at multithreaded reading than the previous one, but is still far from perfect under such load.
As the results of this test suggest, you should not create a multithreaded load on your hard disk drive because most HDDs don’t like that.
Multithreaded writing is easier for modern HDDs thanks to large amounts of cache memory installed in them. An HDD might have run out of cache when the typical cache size used to be 2 megabytes, but now there is almost no difference between 16 and 32 megabytes of cache. Still, we can note that Seagate’s new 7200.12 and LP series drives are the slowest ones in this test.