4 KB Random Performance: RAW, Windows, And Mac
Random Read Performance (background info)
We're used to seeing SSDs built on second-generation SandForce controllers (like the Vertex 3) perform at the head of the pack. By comparison, the Vertex 4 falls behind. Using an 8 GB LBA span, the 256 GB and 512 GB models hover just above the 200 MB/s barrier. It's a bit difficult to see from the graph, but both Vertex 4s offer nearly identical performance. The Vertex 3 still maintains a clear lead, as it's the only SSD capable of punching through the 400 MB/s ceiling at a queue depth of seven.
Once we format our test drives, we see that the performance overhead imposed by a file system is quite considerable. Based on past reviews, we know that physical drive performance should start out at roughly 80-90 MB/s for the 256 GB m4, 256 GB 830, Vertex 3s, and SSD 520s—but that's not what we see here. Formatted, all the tested SSDs start at roughly 20 MB/s.
However, the Vertex 4 does seem to enjoy a slight (10 MB/s) advantage at queue depths higher than four. That gap quickly expands to 70 MB/s after moving up to eight outstanding I/O operations.
Our Windows 7-based system returns relatively strong random read results. At a queue depth of eight, every SSD punches through the 100 MB/s barrier.
This does not hold true on our MacBook Pro, which is limited to sub-100 MB/s speeds. Nevertheless, OCZ's newest SSD slightly leads its competition (by 6 MB/s) at low queue depths. Once you scale up to queue depth of eight, you see the Vertex 4 enjoying a 20 MB/s speed advantage in random reads.
Random Write Performance
The unique nature of SandForce's compression technology requires breaking random write analysis into two parts. Presented with highly compressible data (the sort of information typically handled elegantly by the SandForce-based drives), OCZ's Vertex 4 wrestles away a victory. Particularly at low queue depths, the new Vertex dominates its predecessor.
Incompressible data (denoted by OCZ Vertex 3 240 GB [Random] in the chart above) is the Vertex 3's Achilles' heel, preventing it from exceeding random write speeds above 250 MB/s. The Everest 2 controller does not use this compression-dependent technology, so the Vertex 4 doesn't miss a beat.
Our formatted Mac and PC yield vastly different results. As we saw in the read tests above, the Windows 7-based PC seems much better suited to delivering solid random write performance, and the outcome largely mirrors what we see when we test at the physical block level.
In contrast, the results from our MacBook Pro reflect significantly less performance. Complicating analysis is a very tight grouping. As you can see, OCZ's Vertex 4, Vertex 3, and Samsung's 830 are all pretty similar. The only outlier is Intel's SSD 320, the only SATA 3Gb/s SSD in our charts.