Sequential Read Performance
Except for the Agility 4, all of the SSDs approach 550 MB/s in our sequential read test at a queue depth of four and higher.
Oddly, Samsung's 830 is the fastest performer at a queue depth of one, delivering ~470 MB/s. The 840 Pro isn't too far behind at 410 MB/s, effectively tying the Vertex 4. Meanwhile, the Vertex 3 and m4 appear in the middle of the pack, pushing ~370 MB/s.
OCZ's Agility 4 and Corsair's Neutron GTX start the test lagging, although the Corsair drive quickly ramps up above 500 MB/s at higher queue depths. Unfortunately, OCZ's new mainstream drive appears to get stuck at a maximum throughput just north of 400 MB/s.
Sequential Write Performance
Examples include Application Installation, Document Backup
SandForce's second-gen controllers were the first to saturate the SATA 6Gb/s interface with sequential writes. Crucial's m4 debuted a month later, but could only offer about 60% as much performance. The caveat is that SandForce's drives rely on compression to achieve those numbers. Even in a worst-case scenario, though, the 240 GB Vertex 3 is slightly faster than the m4 when it comes to dealing with incompressible data.
Samsung's previous-generation 830 delivers up to 400 MB/s, which makes it strong competition for SandForce-based drives. However, that's only the case in environments with an even mix between compressible and incompressible data. Presented with completely compressible data, the Vertex 3 rises to the top.
Fortunately, the 840 Pro doesn't force us into all of those conditional statements. It's a notable improvement over the 830, matching what SandForce's technology relies on compressible data to do (except that Samsung can do it all of the time).
The Vertex 4 was the first drive we saw to achieve something along the same lines, and Corsair's Neutron GTX matches both competitors by shooting up to 500 MB/s or so at a queue depth of two. It's amazing what a year or evolution in this segment can do.