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 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 Read, part 3
- IOMeter: Multithreaded Write, part 1
- IOMeter: Multithreaded Write, part 2
- IOMeter: Multithreaded Write, part 3
It is all simple when the HDDs are reading just one data thread. The results are actually the same as in the sequential reading test above. We can only note that the Seagate 15K.5 series is somewhat faster than its contemporaries.
The number of data threads is increased to two, and we can’t but applaud Seagate’s HDDs. Starting from the 15K.5 generation these HDDs are indifferent to a second read thread, refusing to slow down. Fujitsu’s drives and Hitachi’s two latest generations lost about one third of their speed. The addition of a second read thread is too heavy for the first generation of SAS drives, except for the Fujitsu. These oldies slow down more than fourfold!
There are no big changes in the standings when we add more threads. All the Seagate drives, except for the 15K.4, deliver excellent performance whereas the other HDDs are far from perfect.
Writing one thread is not interesting. We’ve seen these results already, including the terribly low performance of the 300GB Fujitsu MBA3 RC. There is only one unclear fact: the 73GB Seagate 15K.5 is very slow writing even one data thread.
Most of the HDDs survive the addition of a second write thread with minimum speed loss. They seem to have not noticed the harder load. Hitachi’s 15K147 and 15K300 series drives even speed up a little. Both series from Fujitsu and the Maxtor slow down more, but it is the Seagate 15K.4 that suffers a real performance hit. That’s another reason for us to praise Seagate for having quickly optimized its server HDDs for such characteristic multithreaded loads.
Again, the overall picture does not change when we add a third and fourth thread.