OCZ has been at the forefront of each generation of SandForce SSD release since the debut of the SF-1500 based Vertex Limited Edition. More recently the Vertex 3 was the first client SSD to use SandForce's SF-2281 controller. Many of you have written me asking if the Vertex 3 is worth the additional cost over the Vertex 2. Given that you can pick up a 120GB Vertex 2 for $210 ($180 after rebate), and a 120GB Vertex 3 will set you back $300 flat it's tough to recommend the latter despite the performance improvements. If you don't have a 6Gbps platform (e.g. Intel 6-series, AMD 8-series) the Vertex 2 vs. Vertex 3 decision is a little easier to make, otherwise the newer, faster Vertex 3 is quite tempting.

There's another issue holding users back from the Vertex 3: capacity. The Vertex 3 is available in 120, 240 and 480GB versions, there is no 60GB model. If you're on a budget or like to plan frequent but rational upgrades, the Vertex 3 can be a tough sell.

Enter the Agility 3, OCZ's mainstream SF-2281 drive.

Architecturally the Agility 3 is identical to the Vertex 3. You get the same controller running similar firmware, and as a result post similar peak performance stats (note the use of the word peak):

OCZ SF-2200 Lineup
Specs (6Gbps) Agility 3 Agility 3 120GB Vertex 3 120GB Agility 3 240GB Vertex 3 240GB Vertex 3 480GB
Raw NAND Capacity 64GB 128GB 128GB 256GB 256GB 512GB
Spare Area ~6.3% ~12.7% ~12.7% ~12.7% ~12.7% ~12.7%
User Capacity 55.8GB 111.8GB 111.8GB 223.5GB 223.5GB 447.0GB
RAISE No Yes Yes Yes Yes Yes
Number of NAND Devices 8 16 16 16 16 16
Number of die per Device 1 1 1 2 2 4
NAND Type ONFI 1.0 ONFI 1.0 ONFI 2.0 ONFI 1.0 ONFI 2.0 ONFI 2.0
Max Read Up to 525 MB/s Up to 525 MB/s Up to 550MB/s Up to 525 MB/s Up to 550MB/s Up to 530MB/s
Max Write Up to 475 MB/s Up to 500 MB/s Up to 500MB/s Up to 500 MB/s Up to 520MB/s Up to 450MB/s
4KB Random Read 10K IOPS 20K IOPS 20K IOPS 35K IOPS 40K IOPS 50K IOPS
4KB Random Write 50K IOPS 50K IOPS 60K IOPS 45K IOPS 60K IOPS 40K IOPS
MSRP $134.99 $229.99 $249.99 $419.99 $499.99 $1799.99
Street Price ? ? $299.99 ? $559.99 $1799.99

OCZ has started publishing both peak and incompressible write performance data, but only on its product sheets. While peak performance isn't affected, incompressible performance is. Using AS-SSD as a benchmark, OCZ claims the Agility 3 is only able to muster about 200MB/s for peak sequential reads/writes on the 240GB drive - that's less than half the score the Vertex 3 gets in AS-SSD's read test. Our benchmarks, as you'll soon see, confirm the deficit.

If it's not the controller causing this, and it's not the firmware - then it's the NAND. The Agility 3 (and Solid 3) both use asynchronous NAND. What does that mean? Let's find out.

Asynchronous NAND: An ONFi History Lesson

It takes 50µs to read 8KB from a 25nm Intel NAND die. That works out to a staggering 156MB/s, from a single NAND die. Even the old 50nm stuff Intel used in the first X25-M could pull 4KB in 50µs or ~78MB/s. The original X25-M had 10 channels of NAND, giving it the ability to push nearly 800MB/s of data. Of course we never saw such speeds, as it's only one thing to read a few KB of data from a NAND array and dump it into a register. It's another thing entirely to transfer that data over an interface to the host controller.


ONFi 1.0 limited NAND performance considerably

Back in 2006 the Open NAND Flash Interface (ONFi) workgroup was formed with the task of defining a standardized interface for NAND Flash. Today, Intel and Micron are the chief supporters of ONFi while Toshiba and Samsung abide by a separate, comparable standard.

As is typically the case, the first standard out of the workgroup featured very limited performance. ONFi 1.0 topped out at 50MB/s, which was clearly the limiting factor in NAND transfer speed (see my example above). The original ONFi spec called for an asynchronous interface, as in one not driven by a clock signal. Most logic these days is synchronous, meaning it operates off of a host clock frequency. Depending on the architecture, all logic within a synchronously clocked system will execute/switch whenever the clock signal goes high, low or both. Asynchronous logic on the other hand looks for a separate signal, similar to a clock, but not widely distributed - more like a simple enable pin. In the asynchronous NAND world this is the role of the RE, WE and CLE (read/write/command-latch enable) signals.

ONFi 2.0 brought the move to source synchronous clocking, as well as double data rate (DDR) operation. Not only were ONFi 2.0 NAND devices tied to a clock frequency, transfers happened on both rising and falling edges of the clock - a similar transition was made in SDRAM over a decade ago. While ONFi 1.0 NAND was good for up to 50MB/s, ONFi 2.0 increased the interface speed to 133MB/s. Present day synchronous ONFi 2.1/2.2 NAND is no longer interface limited as the spec supports 166MB/s and 200MB/s operating modes. Work on ONFi 3.0 is being done now to take the interface up to 400MB/s.

The Agility 3

OCZ sent us a 240GB Agility 3 for review. Inside it looks like this:

You see the SF-2281 controller in its usual spot and to the right of it are eight 25nm Micron NAND devices. Flip the board over and you get another eight.

As always, we look at the part number to tell us what's going on. Micron's part numbers are a little different than Intel's but the key things to pay attention to here are the 128G (128Gbit packages, 16GB per package) and characters 11 and 14. Character 11 here is an F, which corresponds to 2 die per package (2 x 8GB 25nm die in each NAND device) while number 14 is an A, indicating that this is asynchronous NAND. To date I've only encountered 25nm synchronous (represented by the letter B) NAND, but as with any other silicon device there's always a cost savings if you can sacrifice performance.

Equipped with asynchronous NAND, the Agility 3's max performance is limited to 50MB/s per channel compared to 200MB/s per channel in the Vertex 3. The Vertex 3 doesn't come close to saturating its per-channel bandwidth so there's a chance that this change won't make much of a difference. To further tilt things in the Agility 3's favor, remember SandForce's controller throws away around 40% of all of your data thanks to its real time compression/deduplication algorithms - further reducing the NAND bandwidth requirements. When a Vertex 3 pushes 500MB/s that's not actual speed to NAND, it's just how fast the SF controller is completing its tasks. In a typical desktop user workload without too much in the way of incompressible data access, the Agility 3 should perform a lot like a Vertex 3.

Cost Savings and a 60GB Drive

I mentioned the only benefit to asynchronous NAND being a cost savings, if we go by OCZ's MSRPs the savings don't look too great at 120GB: here the Agility 3 is $229.99 vs. $249.99 according to OCZ. Street pricing tells a different (more expensive) story for the Vertex 3. The 120GB drive is more like $299.99, which would mean the Agility 3 (if its MSRP is accurate) would be a full $70 cheaper. Move to 240GB and the gap likely widens.

With the Agility 3, OCZ is also introducing a 60GB model. SandForce's NAND redundancy technology called RAISE, requires an entire NAND die be sacrificed and added to the spare area pool in the event of a NAND failure. At 25nm a single die is 8GB, which would mean a 64GB drive would lose 1/8 of its capacity just due to RAISE. Get rid of another 6.3% of the drive for the standard spare area and you're looking at a pretty high cost per usable gigabyte.

One feature of the SF-2200 firmware however is the ability to disable RAISE. I've never advocated it simply because I like the idea of being able to recover from a failed NAND die in the array, but at the 60GB capacity OCZ felt it was better left turned off (otherwise the drive would have to be sold as a 56GB drive instead).

Entire NAND die failures are pretty rare but it's still possible that one could happen. The 60GB Agility 3, as a result, makes a potential reliability tradeoff for capacity. Personally I'd like to see OCZ offer the option to enable RAISE, although I'm not sure if any user accessible utilities exist that would allow you to do that easily.

The Test

CPU

Intel Core i7 965 running at 3.2GHz (Turbo & EIST Disabled)

Intel Core i7 2600K running at 3.4GHz (Turbo & EIST Disabled) - for AT SB 2011, AS SSD & ATTO

Motherboard:

Intel DX58SO (Intel X58)

Intel H67 Motherboard

Chipset:

Intel X58 + Marvell SATA 6Gbps PCIe

Intel H67
Chipset Drivers:

Intel 9.1.1.1015 + Intel IMSM 8.9

Intel 9.1.1.1015 + Intel RST 10.2

Memory: Qimonda DDR3-1333 4 x 1GB (7-7-7-20)
Video Card: eVGA GeForce GTX 285
Video Drivers: NVIDIA ForceWare 190.38 64-bit
Desktop Resolution: 1920 x 1200
OS: Windows 7 x64

 

Random & Sequential Performance
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  • swaaye - Tuesday, May 24, 2011 - link

    Well I guess we're in for a few year wait yet before SSDs get cheaper. Yikes. :) Come on brilliant process engineers!!!
  • jb510 - Tuesday, May 24, 2011 - link

    If I write 100 MB of compressible data to a SF drive does it use 100MB of space? Ie is it stored compressed or is that just for when it's going through the controller.

    If I compress or encrypt my entire drive on the fly (several utilities exist to do this) how does that affect performance?
  • tecsi - Tuesday, May 24, 2011 - link

    We need to include the $135 60GB and $230 120GB Agility 3s to review. The $500 240GB is clearly a great performing product. But expensive. We need to understand what performance hits, other than capacity, we would take by going with the lower cost devices.

    Presumably the 60GB and 120GB Agility 3s will ship in much higher volume, so it important to include them in the performance charts.
  • JasonInofuentes - Tuesday, May 24, 2011 - link

    It is logical to expect that the difference in speeds between the 240 GB Agility 3 and the 120 GB Agility 3 will mirror that of the respective Vertex 3 drives, since the structural changes are the same (two die per device vs one die per device). In real world usage, this is likely to be noticeable in some instances but not groundbreaking.
  • seapeople - Tuesday, May 24, 2011 - link

    You really must not have been very confident in your AnandTech 2011 Storage Bench if you didn't think you'd have to debut it by MAY.

    Seriously...
  • MilwaukeeMike - Wednesday, May 25, 2011 - link

    That block of text describing the Storage Bench has been pasted into a bunch of reviews. Read some others and you'll see it. I don't know when it first showed up, but it was a few months ago, maybe even last year.
  • ssd123 - Tuesday, May 24, 2011 - link

    Too bad that OCZ is more interested in time-to-market than making reliable products.

    Check out their forums; there is no end of problems with their drives. I've personally experienced it with their Vertex 2 that would blow away my boot partition every 2 weeks or so. The replacement V2 drive they provided had the same problem.

    The solutions they propose to unlucky customers range from updating BIOS, changing registry settings and updating drivers. Often, none of these fixes end up making a difference.

    I love the performance of the OCZ drives, when they are working.

    Unfortunately they do not deliver on the basic requirements of storage devices: they need to read and write data reliably.

    I'm no Intel fanboy but I have to admit their SSDs are rock solid: they install like a regular drive and just work. No registry tuning, no driver issues, no bios problems.

    OCZ has a great forums and a very engaged online community that's more than willing to help; it's a shame that they are so busy...
  • sanguy - Tuesday, May 31, 2011 - link

    We're in the same boat - we want to use Vertex 3 (and prior Vertex 2) for one of our applications that really benefits from SSD performance but the reliability and support OCZ provides is dismal.

    We're using Intel G2 and G3 drives and while not as fast as the Vertex 2/3 they have been 100% reliable with ZERO issues with several hundred of them deployed.

    So I love it when I see people bashing Intel - but I'd gladly give up a bit of performance for my storage to be non-volatile ;)

    SG
  • tecsi - Wednesday, May 25, 2011 - link

    We need to see performance numbers of not only $500 240GB Agility 3, but also $135 60GB and $230 120GB.

    These are clearly economically options for boot/app drives in desktops.
  • tecsi - Wednesday, May 25, 2011 - link

    We need to know how the $135 60GB and $230 120GB Agility 3s fare vis-a-vis their larger, but much more expensive, $500 240GB brother.

    Both the 60GB and 120GB should provide ample capacity for a boot/app SSD.

    This would really complete the picture.

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