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.

Iometer - 4KB Random Write, 8GB LBA Space, QD=3

Peak performance on the 120GB Vertex 3 is just as impressive as the 240GB pre-production sample as well as the m4 we just tested. Write incompressible data and you'll see the downside to having fewer active die, the 120GB drive now delivers 84% of the performance of the 240GB drive. In 3Gbps mode the 240 and 120GB drives are identical.

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:

Iometer - 4KB Random Write, 8GB LBA Space, QD=32

At high queue depths the gap between the 120 and 240GB Vertex 3s grows a little bit when we're looking at incompressible data.

Iometer - 4KB Random Read, QD=3

Random read performance is what suffered the most with the transition from 240GB to 120GB. The 120GB Vertex 3 is slower than the 120GB Corsair Force F120 (SF-1200, similar to the Vertex 2) in our random read test. The Vertex 3 is actually about the same speed as the old Indilinx based Nova V128 here. I'm curious to see how this plays out in our real world tests.

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.

Iometer - 128KB Sequential Write

Highly compressible sequential write speed is identical to the 240GB drive, but use incompressible data and the picture changes dramatically. The 120GB has far fewer NAND die to write to in parallel and in this case manages 76% of the performance of the 240GB drive.

Iometer - 128KB Sequential Read

Sequential read speed is also lower than the 240GB drive. Compared to the SF-1200 drives there's still a big improvement as long as you've got a 6Gbps controller.

The Vertex 3 120GB AnandTech Storage Bench 2011
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  • miscellaneous - Thursday, April 07, 2011 - link

    Given this particularly insidious paragraph:
    "OCZ will also continue to sell the regular Vertex 2. This will be the same sort of grab-bag drive that you get today. There's no guarantee of the NAND inside the drive, just that OCZ will always optimize for cost in this line."

    Will these "grab-bag" drives be using the same SKU(s)/branding as the original - well reviewed - Vertex 2? If so, how is using the _old_ SKU(s) to identify the _new_ "grab-bag" drives, whilst introducing _new_ SKU(s) to help identify drives with the _old_ level of performance a satisfactory solution?
    Reply
  • erple2 - Friday, April 08, 2011 - link

    I believe that the issue is scale. It would not be possible financially for OCZ to issue a massive recall to change the packaging on all existing drives in the marketplace. Particularly given that while the drives have different performance characteristics (I'd like to see what the real world differences are, not just some contrived benchmark), it's not like one drive fails while another works.

    So it sounds to me like they're doing more or less what's right, particularly given the financial difficulty of a widespread recall.
    Reply
  • Dorin Nicolaescu-Musteață - Thursday, April 07, 2011 - link

    IOmeter results for the three NAND types are the same for both compressible and uncompressible data in ”The NAND Matrix”. Yet, the text suggests the opposite. Reply
  • gentlearc - Thursday, April 07, 2011 - link

    The Vertex 3 is slower
    It doesn't last as long
    Performance can vary

    Why would you write an entire article justifying a manufacturers decisions without speaking about how this benefits the consumer?

    The real issue is price and you make no mention of it. If I'm going to buy a car that doesn't go as fast, has a lower safety rating, and the engine can be any of 4 different brands, the thing better be cheaper than what's currently on the market. If the 25nm process allows SSDs to break a price barrier, then that should be the focal point of the article. What is your focal point?

    "Why not just keep using 34nm IMFT NAND? Ultimately that product won't be available. It's like asking for 90nm CPUs today, the whole point to Moore's Law is to transition to smaller manufacturing processes as quickly as possible."

    Pardon? This is not a transistor count issue, it's further down the road. I am surprised you would quote Moore's Law as a reason why we should expect worse from the new generation of SSDs. The inability for a company to address the complications of a die shrink are not the fault of Moore's Law, it's the fault of the company. As you mentioned in your final words, the 250GB will probably be able to take better advantage of the die shrink. Please don't justify manufacturers trying to continue using a one-size-fits-all approach without showing how we, the consumer (your readership), are benefited.
    Reply
  • erple2 - Friday, April 08, 2011 - link

    I think that you've missed the point entirely. The reason why you can't get 34nm IMFT NAND going forwards, is that Intel is ramping that production down in favor of the smaller manufacturing process. They may already have stopped manufacturing those products in bulk. Therefore, the existing 34nm NAND is "dying off". They won't be available in the future.

    The point about Moore's Law - I think Anand may be stretching the meaning of Moore's Law, but ultimately the reason why we get faster, smaller chips is because of cost. It's unclear to me what the justification behind Moore's law is, but ultimately, that's not important to the actual Law itself. It is simply a reflection of the reality of the industry.

    I believe transistor count IS the issue. The more transistors Intel (or whomever) can pack in to a memory module for the same cost to them (thereby increasing capacity), the more likely they are to do that. It is a business, after all. Higher density can be sold to the consumer at a higher price (more GB's = more $'s). Intel (the manufacturer of the memory) doesn't care whether the performance of the chips is lower to some end user. As you say, it's up to the controller manufacturer to figure out how to take into account the "issues" involved in higher density, smaller transistor based memory. If you read the article again, Anand isn't justifying anything - he's simply explaining the reasons behind why RIGHT NOW, 25nm chips are slower on existing SF drives than 34nm chips are.

    It's more an issue of the manufacturers trying to reuse "old" technology for the current product line, until the SF controller optimizations catch up to the smaller NAND.
    Reply
  • gentlearc - Saturday, April 09, 2011 - link

    Once again, why do an article explaining a new product that is inferior to the previous generation with no reason why we should be interested? AMD's Radeon HD 6790 was titled "Coming Up Short At $150" because regardless of the new technology, it offers too little for too much. Where is the same conclusion?

    Yes, this article was an explanation. Anand does a 14-page explanation, saving a recommendation for the future.

    "The performance impact the 120GB sees when working with incompressible data just puts it below what I would consider the next-generation performance threshold."

    The questions remains. Why should the120GB Vertex 3 debut $90 more than it's better performing older brother?
    Reply
  • mpx999 - Sunday, April 10, 2011 - link

    If you have a problem with speed of flash memory then a good choice for you are drives with SLC memory, which doesn't have as much speed limitations. Unfortunately manufacturers severy overprice them, as SLC drives are much more than 2 times more expansive than MLC ones at the same amount GB, despite the fact that the flash is only 2 times more expansive. You can buy reasonably priced (2x MLC version price) SDHC cards with SLC flash, but you can't get reasonably priced (2 x MLC version price) SSD with SLC flash. Reply
  • taltamir - Thursday, April 07, 2011 - link

    "After a dose of public retribution OCZ agreed to allow end users to swap 25nm Vertex 2s for 34nm drives"

    Actually OCZ lets customers swap their 25nm 64Gbit drives for 25nm 32Gbit drives. There are no swaps to the 32nm 32Gbit drives
    Reply
  • garloff - Thursday, April 07, 2011 - link

    Anand -- thanks for your excellent coverage on SSDs -- it's the best that I know of. And I certainly appreciate your work with the vendors, pushing them for higher standards -- something from which everybody benefits.

    One suggestion to write power consumption:
    I can see drives that write faster consume more power -- that's no surprise, as they write to more chips (or the SF controller has to compress more data ...) and it's fair. They are done sooner, going back to idle.
    Why don't you actually publish a Ws/GB number, i.e. write a few Gigs and then measure the energy consumed to do that? That would be very meaningful AFAICT.

    (As a second step, could could also do a mix, by having a bench run for 60s, writing a fixed amount of data and then comparing energy consumption -- faster drives will be longer in idle than slower ones ... that would also be meaningful, but that's maybe a second step. Or you measure the energy consumed in your AS bench, assuming that it transfers a fixed amount of data as opposed to running for a fixed amount of time ...)
    Reply
  • Nihil688 - Thursday, April 07, 2011 - link

    Hello all,
    I am kinda new to all this and since I am about to get a new 6GB/s Sata3 system I need to ask this

    The main two SSDs that I am considering are the Micron's C400 or the OCZ Vertex3 120' version.
    I can see that their sequential speeds in both write and read are completely different with V3 winning
    but their Random IOPSs (always comparing the 120GB V3 and the 128GB C400) differ with C400 winning in reads and V3 winning with big difference in writes.
    I must say I am planning to install my windows 7 OS in this new SSD I am getting and what I would
    consider doing is the following:
    -Compiling
    -Installing 1 game at a time, playing, erasing, redo
    -Maybe Adobe work: Photoshop etc

    So I have other hard drives to store stuff but the SSD would make my work and gaming quite faster.
    The question is, C400 gives 40K of read which is more important for an OS whilst V3 gives better overall stats and is only lacking in random reads. What would be more important for me? Thanks!
    Reply

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