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 speed is good but not 840 Pro level. Some of this can be due to the slower NAND as the queue depth of our random read test is only 3—with higher queue depths the difference between 840 and 840 Pro should be closer.

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

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

Random write speed is a bit odd as performance does not scale up with higher queue depths. Speculating on the cause is difficult, but if I had to guess I would say it's firmware related, not NAND this time. Samsung is most likely doing some very aggressive write combining and caching so it's easy to achieve the same level of performance regardless of queue depth.

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)

Samsung's read centric firmware approach with the 840 really shows off in our low queue depth sequential read test: there is no drive faster than it.

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

Sequential write is pretty poor compared to today's other 256GB SSDs but Samsung is only claiming 250MB/s so this shouldn't come as a surprise. The similarity between random and sequential write speed helps back up what we mentioned earlier: Samsung is likely being very aggressive with its write combining to make random IOs look very sequential.

The Samsung SSD 840 AS-SSD Incompressible Sequential Performance
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  • roedtogsvart - Monday, October 08, 2012 - link

    Might have to finally replace my Intel 320 with this. Very nice review Kristian Reply
  • Old_Fogie_Late_Bloomer - Monday, October 08, 2012 - link

    Both the Intel 320 and the Samsung 840 Pro support encryption...does the non-Pro 840 offer it or not? I'm swinging back towards getting an 840 Pro for my laptop because of the lack of encryption in consumer 830 drives.

    On a side note, I was disappointed to discover recently that my current desktop motherboard doesn't support hard drive passwords, which is a shame given the fact that my system disk (an Intel 320) does...oh well.
    Reply
  • ekon - Monday, October 08, 2012 - link

    The ATA password-based encryption these drives use is beset with issues, flaky motherboard support being just one.

    http://communities.intel.com/thread/20537

    On top of which, it's very poorly documented, and notice how reviews give it nothing more than a passing mention without testing the feature. A TrueCrypt/DiskCryptor alternative it is not :-/
    Reply
  • Samus - Tuesday, October 09, 2012 - link

    I've had my 320 for two years, no problems with encryption, ever.

    And I second roedtogsvart that I may FINALLY replace my aging SSD with one of these. I've been thinking Intel 520 for awhile but still don't trust Sandforce, even with Intel at the helm.

    Samsung and Crucial are keeping the controllers simple, which is why they have the most reliable drives outside of Intel's original X25-M/320 SSD's.
    Reply
  • Old_Fogie_Late_Bloomer - Tuesday, October 09, 2012 - link

    When you say "these drives", do you mean the Intel 320, the Samsung 840 Pro, or both? My T430 supports hard drive passwords for the expressly-stated purpose of allowing for encrypted SSDs, which is why I'm looking at the 840 Pro in particular.

    It seems like the only downsides would be having to enter the password to use the computer, and having to use a motherboard that supports HD passwords to access the drive (so I couldn't just plug it into my current desktop if something were to happen to my laptop and it were off for repair or whatever).
    Reply
  • ruberbacchus - Saturday, October 20, 2012 - link

    On one hand, it seems to me that the potential gains performance-wise with hardware-based rather than software-based encryption are enormous; particularly so on older computers with slower processors. On the other hand, an encryption solution that is not properly documented as well as thoroughly verified and verifiable does simply not exist as a solution; confidence in the implementation is essential to the deployment of encryption. Unfortunately, it seems impossible to obtain clear references to how encryption works in this new class of SSD's. I read somewhere that it should conform to the OPAL standard, which mandates hardware-embedded keys. I am not sure this is such a great idea, for two reasons:
    - the keys will potentially be known to the manufacturer;
    - the keys will be open to physical attacks on the chip controller.
    With TrueCrypt e.g., the user himself generates the encryption keys, the master key used for encrypting the data as well as the header key used to wrap the master key. The latter is tied to the user's password. With hardware-based encryption, passwords may be used for authentication, but the keys will not necessarily be derived from the password. Unchangeable encryption keys weakens the security. In order for the system to be trustworthy, the user should be able to generate and re-generate at will their own encryption keys. At the moment it is not clear this is the case.
    Reply
  • A5 - Monday, October 08, 2012 - link

    I guess I'm old fashioned and don't throw away my laptop every 6 months, but a 3.5 year lifetime seems really really short. Reply
  • crimson117 - Monday, October 08, 2012 - link

    Agreed; maybe for a video card, but I expect longer than 3.5 years out of my hard drives. Reply
  • repoman27 - Monday, October 08, 2012 - link

    Really? I rarely expect a consumer grade HDD to last much longer than that these days. In fact, I've seen an alarming trend of drives failing just past the 2 year mark, and still within the 3 year warranty period. (RMA'd one last week even.) Reply
  • travbrad - Wednesday, October 10, 2012 - link

    I had a 80GB WD that lasted 8 years without failing. I eventually had to stop using it simply because it was too slow. I also had a 250GB WD drive that I used for 5 years (then switched to all SATA). Now I have a 640GB drive that I've been using for almost 4 years. My brother has a couple 500GB drives in his system that have been running for 4-5 years as well.

    Maybe I've just been really lucky, but the only drive I've personally had fail in the last decade was a Hitachi drive (obviously selected for cost not quality) in my HP laptop.

    Now at work it's a different story. Those pre-built machines cut every corner they can to bring costs down so they end up with low quality components (especially PSUs). Even in that situation there is a fairly low number of hard drive failures though (considering how old most of the machines are)
    Reply

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