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.

As impressive as the random read/write speeds were, at low queue depths the Vertex 4's sequential read speed is problematic:

Desktop Iometer - 128KB Sequential Read (4K Aligned)

Curious as to what's going on, I ran AS-SSD and came away with much better results:

Incompressible Sequential Read Performance - AS-SSD

Finally I turn to ATTO, giving me the answer I'm looking for. The Vertex 4's sequential read speed is slow at low queue depths with certain workloads, move to larger transfer sizes or high queue depths and the problem resolves itself:

QD2
QD4
QD8

The problem is that many sequential read operations for client workloads occur at 64 – 128KB transfer sizes, and at a queue depth of 1 - 3. Looking at the ATTO data above you'll see that this is exactly the weak point of the Vertex 4.

I went back to Iometer and varied queue depth with our 128KB sequential read test and got a good characterization of the Vertex 4's large block, sequential read performance:

The Vertex 4 performs better with heavier workloads. While other drives extract enough parallelism to deliver fairly high performance with only a single IO in the queue, the Vertex 4 needs 2 or more for large block sequential reads. Heavier read workloads do wonderfully on the drive, ironically enough it's the lighter workloads that are a problem. It's the exact opposite of what we're used to seeing. As this seemed like a bit of an oversight, I presented OCZ with my data and got some clarification.

Everest 2 was optimized primarily for non-light workloads where higher queuing is to be expected. Extending performance gains to lower queue depths is indeed possible (the Everest 1 based Octane obviously does fine here) but it wasn't deemed a priority for the initial firmware release. OCZ instead felt it was far more important to have a high-end alternative to SandForce in its lineup. Given that we're still seeing some isolated issues on non-Intel SF-2281 drives, the sense of urgency does make sense.

There are two causes for the lower than expected, low queue depth sequential read performance. First, OCZ doesn't currently enable NCQ streaming for queue depths less than 3. This one is a simple fix. Secondly, the Everest 2 doesn't currently allow pipelined read access from more than 8 concurrent NAND die. For larger transfers and queue depths this isn't an issue, but smaller transfers and lower queue depths end up delivering much lower than expected performance.

To confirm that I wasn't crazy and the Vertex 4 was capable of high, real-world sequential read speeds I created a simple test. I took a 3GB archive and copied it from the Vertex 4 to a RAM drive (to eliminate any write speed bottlenecks). The Vertex 4's performance was very good:

Sequential Read - 3GB Archive Copy to RAM Disk

Clearly the Vertex 4 is capable of reading at very high rates – particularly when it matters, however the current firmware doesn't seem tuned for any sort of low queue depth operation.

Both of these issues are apparently being worked on at the time of publication and should be rolled into the next firmware release for the drive (due out sometime in late April). Again, OCZ's aim was to deliver a high-end drive that could be offered as an alternative to the Vertex 3 as quickly as possible.

Update: Many have been reporting that the Vertex 4's performance is dependent on having an active partition on the drive due to its NCQ streaming support. While this is true, it's not the reason you'll see gains in synthetic tests like Iometer. If you don't fill the drive with valid data before conducting read tests, the Vertex 4 returns lower performance numbers. Running Iometer on a live partition requires that the drive is first filled with data before the benchmark runs, similar to what we do for our Iometer read tests anyway. The chart below shows the difference in performance between running an Iometer sequential read test on a physical disk (no partition), an NTFS partition on the same drive and finally the physical disk after all LBAs have been written to:

Notice how the NTFS and RAW+precondition lines are identical, it's because the reason for the performance gain here isn't NCQ streaming but rather the presence of valid data that you're reading back. Most SSDs tend to give unrealistically high performance numbers if you read from them immediately following a secure erase so we always precondition our drives before running Iometer. The Vertex 4 just happens to do the opposite, but this has no bearing on real world performance as you'll always be reading actual files in actual use.

Despite the shortcomings with low queue depth sequential read performance, the Vertex 4 dominated our sequential write tests, even at low queue depths. Only the Samsung SSD 830 is able to compete:

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

Technically the SF-2281 drives equal the Vertex 4's performance, but that's only with highly compressible data. Large sequential writes are very often composed of already compressed data, which makes the real world performance advantage of the Vertex 4 tangible.

Incompressible Sequential Write Performance - AS-SSD

AS-SSD gives us another taste of the performance of incompressible data, which again is very good on the Vertex 4. As far as writes are concerned, there's really no beating the Vertex 4.

Random Read/Write Speed AnandTech Storage Bench 2011
POST A COMMENT

127 Comments

View All Comments

  • rw1986 - Friday, April 6, 2012 - link

    This seems very speculative. OCZ has admitted collaboration with Marvell (for example on their new Kilimanjaro platform for the Z-Drive R5 PCIe SSD).

    here is the link to the OCZ Everest 2 announcement: http://www.ocztechnology.com/aboutocz/press/2012/4...

    In the announcement, OCZ makes some specific claims surrounding Everest 2 -- for example:

    "the Everest 2 SSD controller reduces latency to 0.043ms for read operations and 0.026ms for write operations, yielding an improvement of approximately 80 percent over the previous Everest SSD controller generation"

    "The advanced, multi-level BCH ECC engine with progressive error correction adapts to the specific error characteristics of different NAND devices. The programmable ECC engine achieves an effective correction power of up to 128 bits per 1KB of data while significantly reducing the uncorrectable bit error rate (UBER)."

    The Marvell sheet emphasizes some similar things (high performance, error correction technology) but these are more general claims than what OCZ has listed in their Everest 2 spec sheet.

    Is the foundation of your assumption that Everest 2 is just the 88SS9187 that the spec sheets sound similar? That does not seem conclusive to put it generously
    Reply
  • jwilliams4200 - Saturday, April 7, 2012 - link

    There is no hard evidence that is publicly available since OCZ is keeping it quiet for obvious reasons.

    The Octane uses a rebadged Marvell 88SS9174, and the Vertex 4 uses a rebadged Marvell 88SS9187.
    Reply
  • rw1986 - Saturday, April 7, 2012 - link

    I'm just curious how you can make these claims so authoritatively when, as you say "there is no hard evidence that is publicly available" to support your position.

    What you seem to be suggesting is that OCZ made a 32 million dollar acquisition in April of 2011 (Indilinx) and then decided to simply license and rebadge controllers from Marvell rather than build internally (which is completely contrary to what OCZ has told investors and the public). On a Thursday conference call OCZ's CEO was quite adamant that Everest 2 is completely their IP and will improve their profit margin strucutre as a result (since they don't have to pay a fee to Sandforce for each controller as before). If what you are saying is true then OCZ has misled their investors at best.

    This is a pretty serious accusation you are making here and it would be nice if you had a little more to say in support of it than "trust me, i know." If you were really in a position to know then I doubt you would be posting on the comments section at AT.

    I'd be interested to hear some experts weigh in on this exchange. How could we verify or disprove that the Everest 2 is really not Indilinx but instead a rebadged 9187? Surely some analysis can be done on the ASIC
    Reply
  • jwilliams4200 - Saturday, April 7, 2012 - link

    It isn't very important to me either way, since I have no financial interest. But OCZ has a history of dishonesty, and it bothers me to see them get away it.

    If it is important to you, you could start by contacting the appropriate people at OCZ and asking whether the controllers in the Octane and the Vertex 4 have similar or identical circuits with Marvell controllers.
    Reply
  • jwilliams4200 - Wednesday, April 11, 2012 - link

    http://www.anandtech.com/show/5741/ocz-confirms-oc... Reply
  • hackztor - Friday, April 13, 2012 - link

    Good job on being correct. I think alot of people feel betrayed again by ocz. Last time i will purchase their product no matter what. Reply
  • pookguy88 - Wednesday, April 4, 2012 - link

    so wait, right now they'll (256gb, 512gb) ship with 1gb DRAM but later on 512mb? Is it just me or is that going to be a huge deal for customers once they realize that they basically got jacked 512mb of RAM vs early adopters? Reply
  • pattycake0147 - Wednesday, April 4, 2012 - link

    I inferred that the smaller drives will ship with 1GB but only 512MB will be used on the drive. Reply
  • Voo - Wednesday, April 4, 2012 - link

    Considering that was explicitly stated in the article there's not much to infer here is it?

    "Oh no I was jacked from 512mb that were deactivated anyhow - what a scandal!"
    Reply
  • antef - Wednesday, April 4, 2012 - link

    Why is your standard recommendation still the Samsung SSD 830? Given the performance, prices, and most notably, the incredibly excellent reviews on sites like Newegg, the Crucial M4 would still be my recommendation to new shoppers. Reply

Log in

Don't have an account? Sign up now