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Random Read & Write Patterns

Now we will see the dependence of performance of the drives in random read and write modes on the size of the data block.

We will discuss the results in two ways. For small-size data chunks we will draw graphs showing the dependence of the amount of operations per second on the data chunk size. For large chunks we will compare performance basing on data-transfer rate in megabytes per second.

Reading in small data blocks ranks the HDDs up according to their response time. There are no exceptions. You must note that you shouldn’t rely on the response time as specified by the manufacturer. The results of our test above are far more credible.

The WD drives show team spirit, their graphs nearly coinciding.

It is the sequential read speed which is important here and we don’t have any surprises, either. We can note the good performance of the Samsung F3 and the low (compared with same-class products) results of the Caviar Green series. We’ve got one loser: the Seagate 7200.11 is too slow even for a two-platter model.

We’ve got some interesting things at random writing. First, there is some correlation with the response time results at small data blocks. Second, the HDDs with large amount of cache do not have any advantage. It is not the total cache size but the number of individual requests it can store simultaneously that’s important.

This test is won by the Seagate 7200.11 and WD Blue A7, indicating that the new generation is not best all around. On the losing side we can see the single-platter WD Green with 32MB cache and the Samsung F2 which is especially poor even for its reduced spindle rotation speed.

It is the speed of sequential writing that determines how fast the HDDs write large random-address data blocks. The single-platter 7200RPM models are in the lead, except for the Seagate 7200.12. The Seagate 7200.11 is the slowest among the dual-platter drives.

 
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