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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  • Taft12 - Monday, October 08, 2012 - link

    Who cares?? Frequent firmware updates are a sign of an incompetent engineering and testing. I'll stick with the vendors known for getting it right the first time thank you very much. Reply
  • JuneBugKiller - Monday, October 08, 2012 - link

    If Samsung 840 120GB cost's $109.99 and you can get an OCZ Vertex 4 128GB for $104.99, which is faster in 80% of the benchmarks and is $5 cheaper then who's going to want it? So what if the price goes down to $80, are people going to save $25 thinking their hard drive is going to die twice as fast. I have bought (with works money) around 30 ssd's including Intel 80GB & 160GB Silver Case, Intel 710 100GB, Vertex 3 Max IOPS 120GB and Vertex 4 128. So far I've only had 2 ssd's go bad and they were both Intel 80GB ssd's. One wouldn't power on and the other reported at 8MB. Intel replaced them under warranty.

    The point is I have been buying SSD's for years and I just don't see how anyone would want these samsung ssd's. Samsung is famous for huge margins on each product. When a company pockets $240 off of a $500 tablet and their name isn't Apple then something is wrong.
    Reply
  • JarredWalton - Monday, October 08, 2012 - link

    Wow, talk about skewing the data by cherry picking the worst-case numbers for the 840. The Vertex 4 is only 85% faster in one specific test: AS-SSD Write performance. Of course, in the AS-SSD Read performance it's also 10% faster than the Vertex 4 256GB, but you just ignore that? Samsung also has some of the best SSDs in terms of large reliability figures, so even if the 840 is slightly slower than other drives in some tests, it may be the better option. Also don't forget to factor in that the 840 appears to be well-tuned for light workloads (e.g it's near the top of our light workload results).

    Personally, I think the 840 needs to come in below the current 830 drive prices to make sense, and it probably will not long after the official release. 128GB 830 drives already go for under $100, and 256GB drives have been at $200 for over a month now -- likely all in preparation for the release of the 840. TLC NAND is cheaper to manufacture (per GB), and long-term it will be significantly more profitable for Samsung. Get some good DSPs added into the mix and I wouldn't be surprised to see most SSDs in two generations being TLC based, with MLC moving to the enterprise level and SLC basically going away because it's too expensive.
    Reply
  • JuneBugKiller - Monday, October 08, 2012 - link

    No I'm talking about counting each benchmark add the total and divide the number by how many OCZ Vertex 4 won and it was over 80% of the total number of benchmarks. How is Samsung a better option? TLC over MLC, OCZ fastest drive to Samsungs slowest new drive. Of course Samsung is going to make more profit but why would you want to spend the same amount on a slower drive with less endurance? Reply
  • JarredWalton - Monday, October 08, 2012 - link

    Sorry, 80% of benchmarks is correct; I read that wrong. But let's put that in perspective:
    http://www.anandtech.com/bench/Product/678?vs=628

    If we look at average performance across all benchmarks, the difference between OCZ Vertex 256GB and Samsung 840 250GB is a 12.4% advantage for OCZ. However, OCZ hasn't exactly been free from firmware issues. That right there is the reason many people will pay a bit more for a Samsung (even if it's slower).

    Would I buy an 840 right now for $200 or whatever? Definitely not -- I'd actually take the 830, just for proven reliability over time. Give the 840 a couple months just to be safe, then check the prices. If it's still more expensive than the Vertex 4, sure, go for OCZ if you'd like. If they're the same price, though, the 12% performance is practically meaningless for most consumer workloads.
    Reply
  • sean.crees - Monday, October 08, 2012 - link

    Because it's not just about performance, it's also about reliability. This is user data we are talking about. Even a single loss could be catastrophic. OCZ doesn't have the reliability track record that Samsung and Intel has, and for that reason there are many people who will only ever buy from Samsung or Intel. So then OCZ isn't even mentionable. It doesn't matter if they are faster because who cares if your data is at risk?

    Also you have to consider that the REAL WORLD difference between any modern 6Gbps SSD is negligible, so then performance means even less. It ends up being a contest of reliability instead of a contest of speed. In that contest, OCZ loses.
    Reply
  • krumme - Monday, October 08, 2012 - link

    I would want it :)

    We have about 7-8 ssd in the house, about 3 of those is vertex 3 ssd, and there have been realiability and firmware issues.

    I think ssd speeds since the last 2 years have been good enough and would prioritize reliability any day.

    I had to replace an sandisk u100 in my Samsung 9 series x3c to a faster one, but that was because the u100 was like a return to 4 years ago. Its a good backup now.

    Now hopefully reliability is there, and prices will go down so everyone can afford it. We dont need more firmware updates and shit. Its like the first 3d gfx in the mid 90, - a mess.

    But you are right Samsung is starting to get expensive, and charge for the brand. Wether you like it or not it will certainly mean more Samsung reviews too. Being a big boy, have advantages :)
    Reply
  • Taft12 - Monday, October 08, 2012 - link

    "If Samsung 840 120GB cost's $109.99 and you can get an OCZ Vertex 4 128GB for $104.99, which is faster in 80% of the benchmarks and is $5 cheaper then who's going to want it?"

    A person who values reliability at a value higher than $0 will choose the non-OCZ product every time.
    Reply
  • Jaybus - Thursday, October 11, 2012 - link

    Time will tell. The TLC NAND should end up around 30% cheaper per GB than MLC. Then it will come down to buying a 240 GB MLC for $200 or a 320 GB TLC for the same price. Reply
  • iwod - Tuesday, October 09, 2012 - link

    I would be buying an Intel instead if it cost $109.99. While Sammy is possibly the closest to intel in terms of reliability. I wouldn't want a TLC SSD for the same price. And the difference would be marginal anyway. I could feel the difference between a decent 3Gbps SSD and 6Gbps SSD, i am not sure if there is anything to feel for two decent 6Gbps SSD.

    Now if the retail price is really in the range of $70 - 80 that would be a huge difference. Because you are essentially choosing the second best reliable SSD for decent performance and cheapest price.
    Reply

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