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.

Desktop Iometer - 4KB Random Read (4K Aligned)

Random read performance was a strong suit of the old C300 and Crucial scaled back on it a bit when building the m4's firmware. The 0009 firmware improves performance a little bit but not tremendously. As we've seen in our previous reviews however, for desktop users being able to hit over 60MB/s in 4KB random reads doesn't translate into real world performance gains. All of the drives here do very well.

Desktop Iometer - 4KB Random Write (4K Aligned) - 8GB LBA Space

Random write performance also improved a little bit post update. The m4 is still incredibly fast here, easily the second fastest drive we've tested.

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:

Desktop Iometer - 4KB Random Write (8GB LBA Space QD=32)

Crucial's performance doesn't scale up with higher queue depths like SandForce's. That's mostly because with highly compressible data sets, SF's drives don't actually write more as queue depth goes up. The controller has to do more deduping but as long as it can keep up, performance looks like it increases while physical writes to NAND don't. Most random writes on a desktop machine are going to be highly compressible, however most desktop workloads won't see sustained 4KB random writes at a queue depth of 32.

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.

Desktop Iometer - 128KB Sequential Read (4K Aligned)

Here's where we see some huge gains. The original m4 firmware posted sequential read performance lower than the C300. With the update to FW0009, performance now surpasses the C300 and comes in just slightly behind Intel's SSD 510.

Desktop Iometer - 128KB Sequential Write (4K Aligned)

Sequential write performance sees a small gain but nothing major here.


The Crucial m4 Update AS-SSD Incompressible Sequential Performance
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  • Carlu - Sunday, September 18, 2011 - link

    You self have recommended and the Intel SSD 320 have gain a lot of credit for it's reliability. Since this is debated i think you leave out Intels complete SSD disk is bad... and give the performance a to important role. No disk is useful if you loose the data on it...
  • hoangcodo - Friday, December 9, 2011 - link

    You to help me with
    I bought Crucial SSD SSD 512 GB M4, yesterday is still attached to the SERVER received, read, save data normally but today it does not grease the machine up to store data, not to delete data. The way you see the fix on my answer helps, thank you.
  • alan1476 - Sunday, April 1, 2012 - link

    You can now get a 256gb Crucial M4 for 289.00 on Amazon, and the prices will drip fuether when OCZ releases their new Vertex 4.
  • ljmichael - Sunday, June 17, 2012 - link

    After read the full information about Crucial m4 SSD, do you want to get it free? Now, AOMEI Tehc offers you a chance to free get this SSD. Read more details information about this event named "Share then Win" from
  • Scour - Monday, September 3, 2012 - link

    Anyone tested the GC with this FW?

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