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Mercury Accelsior PCIe SSD — Speed vs Capacity and Data Type (480GB)
The results shown below are for the 240GB OWC Mercury Accelsior, which has 2 X 120GB SSD modules installed on the PCIe card. Performance might be even higher with the 480GB model.
See the graph below.
The performance is outstanding, and notably better with incompressible writes than the 240GB model. However, real-world usage shows that the actual write speed performance gains are quite modest, see the diglloydHuge test.
The graph captures an interesting initial-use hiccup in the write speed of incompressible data at about the 780 offset (orange line). Note that a “seasoned” drive offers somewhat lower (average) but consistent performance across the drive (gray line). The same behavior is noted with the 240GB model, a persuasive argument that it has to do with the Sandforce controller‘s reaction to incompressible data.
Click for a larger graph.
With a striped pair (cards tested after the single-card tests and were thus “seasoned”), consistent speed is seen for both compressible and incompressible data across the entire drive, almost, except for the initial write-speed oddity.
Reasons for the initially lower performance near “0” seen below for incompressible writes are unclear, but the Sandforce controller does some background housekeeping, and it’s possible that the test was started while it was performing some housekeeping task (pure speculation here).