Articles: Storage
 

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Disk Response Time and Average Positioning Speed

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.

The response time diagram shows a couple of interesting things. First, the 7200RPM drives do not enjoy any serious advantage in terms of read response. Yes, they are in the lead, but the 500GB drive from WD is just as good as them, the Samsung M7E following close behind. Second, the transition to 320GB platters has not increased the response time as we might have feared after our tests of 3.5-inch HDDs. It looks like the new platters are free from such compromises.

When it comes to writing, the Seagate 7200.4 shows a very high response time. This parameter is even higher with the WD drives that have Advanced Format, but at least they have an excuse for that. Due to their physical structure with 4KB sectors, they have to process a 512-byte write request in the following way: first they read the whole sector, then change the required 512 bytes in it, and only then they write the whole changed sector back to the platter.

 
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