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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.

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, and the traditional measurement of speed in megabytes per second becomes more relevant.

Let’s start with reading.

IOMeter: Random Read, operations per second

The 160GB Intel X25-M is in the lead, followed by its 80GB series mate. The Corsair and the Intel X25-E are slower than the leaders, the SLC-based model proving to be the slowest.

Besides comparing the SSDs between each other, take note of the numbers. Thousands of operations per second! Ordinary desktop HDDs cannot deliver even a hundred operations per second in this test whereas the best HDDs, 15,000rpm models with SAS interface and fast heads, can barely notch 200. It is the performance at random-address operations, which is determined by the drive’s access time, is the trump of flash memory based storage. Being limited by the mechanism of the heads and the rotation speed of the platters, hard disk drives cannot compete on this point.

IOMeter: Random Read, megabytes per second

SSDs reach their maximum speed very soon on large data blocks. Again, the two Intel X25-M series models are in the lead whereas the SLC-based model is the slowest.

IOMeter: Random Write, operations per second

The results of this test are far from similar. The two models of the X25-M series perform brilliantly, boasting an excellent performance growth as the data block gets smaller. This is due to the controller and its algorithms, of course. Flash memory proper does not have any exceptional capabilities in terms of random-address writing.

Interestingly, the SLC-based Intel X25-E is overall somewhat slower than its opponents. It only has an advantage on rather large data blocks. The Corsair is poor in this test: Intel’s controller is superior as yet. On the other hand, an HDD would be even slower here. We can recall early SSDs again: they used to be inferior to HDDs in this test.

IOMeter: Random Write, megabytes per second

The SLC-based SSD is beyond competition on large data blocks. The Corsair is much slower than the MLC-based models from Intel until very large data blocks.

 
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