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 has not been dramatically improved. In fact, the mSATA version actually takes a small hit (~12%).

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

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

Random write speed, on the other hand, is substantially better. We are still nowhere near SandForce or OCZ Vector numbers but at least the performance is no longer sub-par. The performance also finally scales up as the queue depth increases (at least for the 2.5" model). The scaling could be more aggressive at higher QDs but I'll rather take good low QD performance as that will have a bigger impact in real world performance where most IOs are between QDs of 1 and 5.

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)

Sequential performance is also very good. Surprisingly the BP4 mSATA is again slower in write performance than the BP3 and compared to the 2.5" BP4, there is quite a big difference.

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

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.

Incompressible Sequential Read Performance—AS-SSD

Incompressible Sequential Write Performance—AS-SSD

Introduction Performance Consistency
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  • watersb - Wednesday, April 3, 2013 - link

    Excellent. I shall purchase the 512GB!
  • Death666Angel - Wednesday, April 3, 2013 - link

    Well, the availability in Europe seems crappy (only one UK shop 35% higher priced than the Samsung 840). I don't understand why the mSATA version is so under performing either. All-in-all, not something I would buy.
  • MyDigitalSSD - Thursday, April 4, 2013 - link

    mSATA uses 4 channels (can only fit 4 chips on board) on an 8 channel controller while the 2.5" uses all 8 channels. You will never notice a difference in daily use.
  • Oxford Guy - Thursday, April 4, 2013 - link

    "The Samsung SSD 840 has really been the only budget drive without any serious drawbacks."

    HardOCP's review of the 120 GB TLC drive found that its read speed plummeted because of testing, indicating that the low lifespan of the TLC NAND can be a problem. That is in addition to not very impressive write speed.
  • MyDigitalSSD - Thursday, April 4, 2013 - link

    Good point. We only use the best Toshiba MLC toggle (synch) flash. Our BP4 performance over time will not deteriorate at all. This drive is a great alternative to Samsung for sure.
  • pcrusan - Thursday, April 4, 2013 - link

    Where is the 240GB BP4 at $160? I find it at $180 and $200.
  • MyDigitalSSD - Thursday, April 4, 2013 - link

    Low stock is causing the temporary pricing fluctuations. There is a serious flash shortage right now.
  • MyDigitalSSD - Thursday, April 4, 2013 - link

    They are in stock at MyDigitalDiscount.com at 159.99!
  • AKFlyerFan - Friday, April 5, 2013 - link

    I just ordered one of the last two reported in stock there, so we'll see how good they are when it comes in and I get it up and running..
  • pcrusan - Tuesday, April 9, 2013 - link

    Now $179.99.

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