SanDisk Extreme II Review (480GB, 240GB, 120GB)

Random Read/Write Speed

The four corners of SSD performance are as follows: random read, random write, sequential read and sequential write speed. Random accesses are generally small in size, while sequential accesses tend to be larger and thus we have the four Iometer tests we use in all of our reviews.

Our first test writes 4KB in a completely random pattern over an 8GB space of the drive to simulate the sort of random access that you'd see on an OS drive (even this is more stressful than a normal desktop user would see). I perform three concurrent IOs and run the test for 3 minutes. The results reported are in average MB/s over the entire time. We use both standard pseudo randomly generated data for each write as well as fully random data to show you both the maximum and minimum performance offered by SandForce based drives in these tests. The average performance of SF drives will likely be somewhere in between the two values for each drive you see in the graphs. For an understanding of why this matters, read our original SandForce article.

If we look at the raw random read/write speed, SanDisk does fairly well but not quite to the level of Samsung's SSD 840 Pro.

Sequential Read/Write Speed

To measure sequential performance I ran a 1 minute long 128KB sequential test over the entire span of the drive at a queue depth of 1. The results reported are in average MB/s over the entire test length. Sequential IO performance is very good on the Extreme II, effectively equalling the performance of Samsung's SSD 840 Pro.

AS-SSD Incompressible Sequential Read/Write Performance

The AS-SSD sequential benchmark uses incompressible data for all of its transfers. The result is a pretty big reduction in sequential write speed on SandForce based controllers.

As a client focused drive, it's no susprise that the Extreme II does well in all of the sequential tests. I did notice consistently higher sequential read performance on the lower capacity Extreme II for some reason, but the gap isn't large enough to be significant. On the sequential write side, the 120GB drive is appreciably slower than the 240 and 480GB models simply because of the reduction in NAND die count.