Sign in with
Sign up | Sign in

4 KB Random Performance: Response Time

The OCZ RevoDrive 3 X2 Preview: Second-Gen SandForce Goes PCIe
By

It's really wrong to look at data rates (throughput) without taking latency and processing time into account. We're explained this before in tablet reviews with regard to WiFi throughput, but the same concept also applies to storage. Let's go back to the analogy of a phone call, because it easily illustrates why there's more to speed than just throughput.

Throughput is the audio quality. Latency is the amount of time from when you speak into the phone until the person on the other side hears you, and processing time is the delay for the person on the other line to think about what you said before answering back. If we apply this to SSDs, throughput is the amount of data you can send over time, latency is the lag due to data transmission, while processing time is the overhead incurred by the SSD when it receives the data.

Now consider that latency plus processing time equals response time. That's really what we're measuring in Iometer. This is a little confusing because Iometer uses the terms latency and response time interchangeably, but it's really only capable of measuring the latter.

In random reads, the RevoDrive 3 X2 has a response time of .14 ms, which is about 40% slower than the RevoDrive X2. Interestingly, the Vertex 3 is the slowest SSD with a response time of 0.17 ms.

Write response time is another matter. The 240 GB Vertex 3, 256 GB m4, 512 GB m4, and both RevoDrives tie for the top spot with a response time of 0.07 ms.

Keep in mind that response time is a measure of the difference between initiating and completing an operation, while throughput is a measure of the amount of data transferred. These two values affect performance in different ways, but they don't stack up. So it's not like the 64 GB drive "feels" 75% slower than the 128 GB drive (25% slower throughput + 50% slower response time). Throughput and response time are usually correlated, in that you get high throughput with low response time. In the event that they don't, it's more like having a high-quality phone call with a long lag time or vice versa.

The max response time offers a look at the extremes. In random reads, the RevoDrive 3 X2 only beats out the 5400.6 Seagate hard drive. That's about 6x slower than the RevoDrive X2 and Vertex 3.

All of the OCZ SSDs fall behind once we look at the maximum write response time, though you need to keep this in perspective. The improvement over a hard drive is what you'll experience most viscerally, rather than the difference between a Vertex 3 and an m4.

OCZ uses SandForce controllers, which means there's a little garbage collection occurring after every write op. RevoDrive 3 X2 doesn't really seem all that different from what we from its predecessor, which suggests that OCZ didn't change its algorithms to the point of affecting performance in this metric.

Display all 37 comments.
This thread is closed for comments
  • 3 Hide
    reyshan , June 28, 2011 10:26 AM
    YoT!damn fast ssd and damn expensive ssd. might buy one 5 years from now(pci-e kind).
  • 2 Hide
    KingArcher , June 28, 2011 4:15 PM
    Wish I had won a lottery :) 
    So that I could afford me some drives like these.
  • 6 Hide
    Why_Me , June 28, 2011 4:29 PM
    omg this drive is fast! But way out of my budget :( 
  • 4 Hide
    warmon6 , June 28, 2011 4:30 PM
    Quote:
    It's not a business-class product. It's for the power user who is able to tax it using the right workload. If you're not one of those folks, the RevoDrive 3 X2 is seriously overkill.


    OVERKILL?!?!

    Nothing is overkill in the computer arena in terms of performance. :p 

    Just the price can be over kill. o.0
  • 7 Hide
    julius 85 , June 28, 2011 4:34 PM
    Just the price can be over kill. o.0

    For me the price is a bottleneck :) 
  • 7 Hide
    ElectroGoofy , June 28, 2011 4:39 PM
    Dear Santa...
  • 2 Hide
    acku , June 28, 2011 4:42 PM
    Santa is going to need a bigger expense account... :) 

    Personally, I'm hoping that OCZ adds TRIM prior to September.

    Cheers,
    Andrew Ku
    TomsHardware.com
  • -1 Hide
    chefboyeb , June 28, 2011 5:21 PM
    Jesus!
  • -2 Hide
    greenrider02 , June 28, 2011 5:43 PM
    I saw defense of the Vertex 3's occasional low numbers, but no mention of the solid (and sometimes better) performance that the cheaper and more miserly Crucial m4 showed throughout your tests.

    Perhaps you have some bias towards the Vertex 3 that needs reconsideration?

    Other than that, $700 seems like a fair price when considering the performace difference, especially if utilized properly, for instance as a high traffic web/corporate server
  • 0 Hide
    acku , June 28, 2011 5:51 PM
    greenrider02I saw defense of the Vertex 3's occasional low numbers, but no mention of the solid (and sometimes better) performance that the cheaper and more miserly Crucial m4 showed throughout your tests.Perhaps you have some bias towards the Vertex 3 that needs reconsideration?Other than that, $700 seems like a fair price when considering the performace difference, especially if utilized properly, for instance as a high traffic web/corporate server


    If you read the first page then you know that I give a nod to Vertex 3s as the fastest MLC based 2.5" SSD. I consider that plenty of love. :) .

    We'll discuss the lower capacity m4s in another article. FYI, I suggest that you read page 5 and page 6. We are not testing FOB. We are testing steady state. That's part of the reason the SF-based drives are behaving differently with incompressible data.

    On your second point, this is in no way targeted toward an enterprise environment (that's what Z-drives are for). There is no redundancy in the array if a single SF controller fails. The whole card is a dud afterward. You can add higher level redundancy, but enterprise customers have so far been nervous on SandForce products. Plus, there's a general preference for hardware vs. software redundancy. (That's them talking not me). Overall, this makes it unacceptable for any enterprise class workload.




  • 0 Hide
    Supertrek32 , June 28, 2011 5:54 PM
    You know, almost any application that would actually benefit from these speeds won't be very effective on these drives. Why? Not enough storage space.

    It's like having a car that can do 300 miles an hour, but can only carry enough fuel to go 20 miles. Does it have a niche? Yeah. Is it practical? Not really.
  • 0 Hide
    cronos177 , June 28, 2011 6:13 PM
    In a couple of years I see them for like 1/2 the price. ONLY worth it for people who earn their paychecks based on the ability to finish task faster. that's the sole purpose at the moment.
  • 1 Hide
    guzami77 , June 28, 2011 6:16 PM
    I have the X2 100GB... im not that impressed. The speed isnt meeting specs, and other hardware/software doesnt always like a PCIe(non-standard) hard drive. Also dont forget you cant overclock your PCIe voltage with one of these...
  • 0 Hide
    acku , June 28, 2011 6:18 PM
    guzami77I have the X2 100GB... im not that impressed. The speed isnt meeting specs, and other hardware/software doesnt always like a PCIe(non-standard) hard drive. Also dont forget you cant overclock your PCIe voltage with one of these...


    I really recommend that you update the firmware. I do notice a speed difference. If you've seen our compressible benchmarks, then you know that over time the RevoDrive X2 can perform poorly. The lack of TRIM doesn't help. :( 
  • 1 Hide
    chefboyeb , June 28, 2011 6:20 PM
    The prices are too steep tho...
  • 0 Hide
    compton , June 28, 2011 6:36 PM
    This is an excellent exploration of SSD performance in general. Without the benefit of storage benches I myself have been wondering why one of my SSDs seems so much faster that the other, when it seems at face value that the answer should be clear.

    As far as OCZ goes, people who can benefit from this drive are a small group, but I'm not exactly sure who that is. Sure, its fantastically fast, and faster is better, but most people would tragically under-utilize a product like this. Since it's clearly not for enterprise use, I just have to guess what a typical user looks like for this device. Is it the high end media creation freelancer? Someone who makes their bones with Photoshop? Who knows? I want one, even though I'd clearly be better served by a more pedestrian drive. It's clearly destined for the "Cool Wall".
  • 2 Hide
    acku , June 28, 2011 6:43 PM
    Ok. I feel like I need to clear up some confusion. Some sites are reporting TRIM support and we're saying there is no TRIM support.

    The RevoDrive 3 X2 has hardware support for TRIM through VCA 2.0. This much is true, but you can't use TRIM because of a software problem. As for why?

    OCZ has a problem getting the TRIM command to the RevoDrive 3 X2, because it uses SCSI commands over PCIe, hence StorPort SCSI drivers. The TRIM command is out of the question because it's technically part of SATA. The only alternative is Unmap, which is to SCSI what TRIM is to SATA. Unfortunately, Windows does not support Unmap as part of its native driver stack. Furthermore, TRIM commands are only issued by Windows 7 when you empty the Recycle Bin, but you must have your SSD set to AHCI (part of SATA). Obviously this different from SCSI. So effectively no TRIM. :( 

    We have been in contact with the Windows driver team and OCZ, so we know that a fix is being explored. If it materializes, that's another matter....

    (RevoDrive and RevoDrive X2 don't don't support TRIM at the hardware level, so the issue is moot for them.)

    Cheers,
    Andrew Ku
    TomsHardware.com
  • 2 Hide
    Niva , June 28, 2011 6:47 PM
    Ideal user would run massive databases that need tons of accesses all the time. Are there drivers for linux for this? Small business server with the right usage will make this worth it. Also the 'trim' issue should be a non-issue under linux whereas win 7 apparently doesn't include the unmap command.
  • 2 Hide
    christop , June 28, 2011 9:05 PM
    Crazy fast!!!
  • 0 Hide
    warmon6 , June 28, 2011 9:45 PM
    __-_-_-__$700?! wow that's a nice price. Though performance @1.25gbps is kind of low for a pci-e solution. there's already on the market +2gbps. anyway those cost +$7000!I'm going to wait and see if there's any defect with this ssd's...


    Where you get Gbps (= Gigabits) from? ;)  http://en.wikipedia.org/wiki/Data_rate_units#Suffix:_b_vs_B

    Were talking about GBps (Gigabytes). :p 
Display more comments