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Sequential Performance Versus Transfer Size

Second-Gen SandForce: Seven 120 GB SSDs Rounded Up
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All of our sequential transfer tests in Iometer are run at a queue depth of one in order to represent the most typical desktop workloads. It's not hard to imagine a situation where an enthusiast might subject an SSD to higher queue depths, though. And indeed, that's where an SSD really stands apart from a conventional hard drive.

Here we're using ATTO to test the sequential reads/writes over 2 GB, starting with a queue depth of two. Why only a queue depth of two? Even when you're pushing more taxing workloads, I/O commands are handled so much faster on an SSD that queue depths higher than two or three are far less common on an average desktop.

The other reason to use ATTO is its ability to easily test different transfer sizes. While 128 KB is fairly standard for measuring sequential performance, larger or smaller transfers are of course relevant still.

Using a queue depth of two, there's very little range between the second-gen SandForce drives. There is, however, a margin of ±50 MB/s in the larger transfer size tests.

When it comes to evaluating sequential writes, there's virtually no difference between the Vertex 3, Agility 3, Solid 3, S511, Wildfire, Chronos Deluxe, and Force 3.

Turning up the queue depth to four doesn't change much with regard to the SandForce-based drives. Overall, we're still looking at similar performance across transfer sizes with a margin of ± 50 MB/s, depending on the drive in question.

We still see the same behavior in sequential writes, regardless of whether the queue depth is two or four.

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