Incompressible Sequential Write Performance: SandForce's Weakness
SandForce’s DuraWrite technology handles compressible data very efficiently, but there are real world cases where you you move incompressible information, whether you know it or not.
Random Write Performance, Incompressible
Examples include file compression and encryption
Writing incompressible data in a random manner is one of the worst things you can do to a SandForce-based SSD. The type of data, first of all, completely circumvents the controller's architectural advantage. Second, random access is inherently slower than sequential.
Consequently, Crucial's 64 GB m4 turns in the most impressive numbers at a queue depth of two or greater. At a queue depth of one, the SandForce-based drives featuring synchronous NAND enjoy a ~10 MB/s advantage over the competition. Meanwhile, the SandForce-based drives armed with asynchronous flash are roughly on par with the 64 GB Crucial m4 and Samsung 830.
Incompressible Sequential Write Performance
Examples include copying/creating multimedia, archive manipulation, encryption, some gameplay, and video recording
Even writing incompressible data sequentially isn't SandForce-friendly. Theoretically, this benchmark should yield a good idea of how various NAND interfaces behave. And indeed, you see drives clump together based on the type of memory they use (the differences almost assuredly aren't attributable to firmware optimizations). Within the clusters, there's only about 4 MB/s separating the models, and of course those numbers are indistinguishable in the real world.
Crucial’s 64 m4 makes for an interesting comparison point because it employs synchronous NAND as well. Its performance advantage suggests that Marvell's controller is simply more adept at writing sequential data once the benefits of compression are factored out SandForce's results. Samsung’s 64 GB 830 blitzes to the top of the chart with a sequential write speed of ~170 MB/s. That’s more than twice as fast as the SandForce-based SSDs with asynchronous flash and 90% faster than those using synchronous NAND.
