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

The speeds are directly proportional to the HDDs’ access time, so the 500GB model from Western Digital is ahead of its opponents.

IOMeter: Random Read, megabytes per second

When the data chunks are larger, the sequential read speed becomes the decisive factor. This helps the Samsung leave the models with 160GB platters behind and take second place.

IOMeter: Random Write, operations per second

Western Digital’s products have no rivals when writing in small data blocks. As for the losers, the Samsung is slower on the smallest data chunks but the Hitachi slows down on larger ones.

IOMeter: Random Write, megabytes per second

The HDDs from Western Digital are superior when writing in large data blocks, too. This manufacturer’s 2.5-inch HDDs have been very fast at writing for a long time. People at Western Digital seem to know some secret.

The Samsung and Hitachi are competing still: the Hitachi is on the losing side through most of the tests but the higher-density Samsung suddenly loses its ground on very large data chunks.