Random Read & Write Patterns

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

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 depending on data-transfer rate in megabytes per second. This approach helps us evaluate the disk subsystem’s performance in two typical scenarios: working with small data chunks is typical for databases. The amount of operations per second is more important than sheer speed then. Working with large data blocks is nearly the same as working with small files where the traditional measurement of speed in megabytes per second becomes more relevant.

Let’s start with reading.

IOMeter: Random Read, operations per second

Oddly enough, the previous-generation HDDs take two top places when reading random-address data in small blocks. They enjoy a considerable lead over the new products. This must be the tradeoff for the increased recording density: the new drives take more time to find the necessary point on the platters. Here, the 7200rpm 2.5-inch drives are much faster than both the 5400rpm 2.5-inchers and the 3.5-inchers. By the way, the 3.5-inch Seagate 7200.11 looks especially poor in this test.

IOMeter: Random Read, megabytes per second

As the data chunk grows up to 1 megabyte and larger, it is the sequential read speed that affects a drive’s performance. As a result, the 3.5-inch products go ahead, the old generation of 2.5-inchers falls behind, and the Seagate 7200.3 is faster than the Western Digital Scorpio Black.

IOMeter: Random Write, operations per second

Efficient deferred writing is important for writing in small data blocks. The resulting picture is funny enough: we’ve got such different leaders as Seagate 7200.11 and Western Digital Scorpio Blue. As for the heroes of this review, the Scorpio Black is close to the leaders while the Momentus 7200.3 is last and much slower even than its predecessor Seagate Momentus 7200.2. Seagate’s “fast” compact series seems to be no good at caching.

IOMeter: Random Write, megabytes per second

It is the drive’s sequential speed that comes into play again. As a result, the HDDs rank up exactly as they did in the IOMeter: Sequential Write test.