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.

The Ultra Plus gets off to a good start, doing very well in our low queue depth random read test, bested only by Samsung's SSD 840 Pro out of our list of contenders here.

Random write performance is pretty good but the Ultra Plus doesn't hit any of the insanely high speeds set by most of the modern drives. Note that its performance is equal to the Samsung SSD 830, which was a favorite of ours. Not having a first class showing here isn't a huge problem.

Many of you have asked for random write performance at higher queue depths. What I have below is our 4KB random write test performed at a queue depth of 32 instead of 3. While the vast majority of desktop usage models experience queue depths of 0 - 5, higher depths are possible in heavy I/O (and multi-user) workloads:

We don't see much scaling with higher queue depths, likely a limit of the Marvell SS889175's 4-channel implementation here.

Steady State 4KB Random Write Performance

SanDisk has a completely separate division that handles enterprise drives, but I was curious to see what steady state 4KB random write performance using a 100% LBA span would look like. To find out I borrowed from our Enterprise Storage tests and compared to the results from our OCZ Vector review. Note that many of these drives are enterprise focused and as a result do much better so don't get too turned off by the comparison:

The Ultra Plus fares much better than I expected, nipping at the heels of the Vertex 4. The Vertex 4 used similar Marvell silicon so I'm not too surprised here.

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.

Like most drive vendors looking to address the light use client market, SanDisk's sequential read performance is actually really good.

Low queue depth sequential write speed is also quite competitive, both of these will help deliver a pretty decent client experience.

AS-SSD Incompressible Sequential 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.

Higher queue depth sequential IO is still very good on the Ultra Plus. There's no penalty to using incompressible data as the controller does no real time data compression/de-duplication.