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Disk Response Time

For 10 minutes IOMeter is sending a stream of requests to read and write 512-byte data blocks with a request queue of 1. The total of requests processed by the HDD is much larger than its cache, so we get a sustained response time that doesn’t depend on the HDD’s buffer size.

The Hitachi C10K147 and the Seagate 10K.2 turn in the best response time at reading among the 10,000rpm models but the gap from the others is quite negligible. As expected, the Seagate 15K.1 is unrivalled as its 50% higher spindle speed is hard to beat. It is interesting to compare the results of the 2.5-inch SAS drives with those of their 3.5-inch counterparts. Referring to the appropriate section of our previous roundup, you can see that the 2.5-inch products are but slightly inferior to their full-size opponents, the spindle rotation speed being the same. This is no wonder actually. It is only with the “slow” 2.5-inch drives with a spindle rotation speed of 5400rpm and 7200rpm that the access time is usually higher because their read/write heads are slowed down to reduce noise and the mass of the actuator. When it comes to server-oriented SAS drives, there is no talking about slowing anything down deliberately. Thus, the compact 2.5-inch models can work quite easily where a low response time is needed.

Most of them also deliver a good response time at writing. The Seagate 15K.1 is the only model to have some problems. It seems to have no deferred writing at all.

 
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