Articles: Storage

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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 each HDD is much larger than its cache, so we get a sustained response time that doesn’t depend on the HDD’s buffer size.

Western Digital’s Caviar Black series drives are still the best when it comes to response time at both reading and writing. The newer model has even improved a little more.

The second team place goes to Hitachi, the older 1000.B being somewhat better at reading and the newer 1000.C much faster at writing.

Samsung’s products are generally not very good in this test, and this time around its 7200RPM HDDs are just a little faster than Western Digital’s 5400RPM ones. The EcoGreen F2 has the highest response time at reading among all these drives. The only good news for Samsung is that the F3 is somewhat better than the F1.

Take note of the P8-indexed WD10EADS. Despite its lower spindle speed (5000 RPM), it is about 0.5 milliseconds better than the M2 model. So, it has reduced-diameter platters indeed.

The WD10EARS has to emulate 512-byte sectors and is a little slower than same-class HDDs at reading, but its writing result is downright poor. It has to read a full physical sector to change one eighth of its data, and this is the outcome of such inefficiency.

Next goes the test of average positioning speed. The drive is being bombarded with read requests like in the response time test, and we calculate the difference between the LBA addresses of the previous and next requests and divide it by the time it took to perform the request. In other words, we have the distance (in gigabytes) the drive’s heads can run through in 1 second.

This test is sensitive to recording density, but Western Digital’s Caviar Black are superior nonetheless. Their swift read/write heads make up for the lower recording density. The Hitachi 1000.C is rather too bad here. It is a shame for a 7200RPM drive with 500GB platters to have last place in the competition. The WD10EADS P8 feels much better. Its smaller-diameter and high-density platters make up for its low spindle rotation speed.

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