The Generic MLC SSD Problem in the Real World

Based on the Iometer results I knew for sure that there was an issue with random write performance on these SSDs, the only common thread between them being the type of controller (JMicron JMF602) and the MLC flash devices being used (Samsung). But I wanted to see if I could get the high latency writes to appear in a real-world benchmark-able way.


The Samsung SLC controller

 

The first indication that something is wrong actually comes from running the Windows Vista install itself, the MLC drive takes 25% longer to complete the install (let’s just ignore the part about the full install not being fully functional upon completion). Clearly there’s an issue with write speed. I ran into something similar with OS X, but I didn't put it together until now.

The problems are far worse in Vista. While OS X will just pause until the data is written, Vista doesn’t seem to respond well to unusually long file write delays. I haven’t been able to get the Vista install to complete without errors on the OCZ Core drive. One install completed but I was greeted with this error as soon as I hit the desktop:

Trying to reinstall gave me this error even before I booted into Vista:

It looks like the Vista install doesn’t do well with significant delays when writing files to the disk. The only way I could actually get a reliable Vista install on the Core drive was by cloning another drive with a working Vista image on it.

For the next test I tried creating a 200MB archive of pictures:

 

So far, so good. The OCZ Core performs no differently than the rest of the pack. Now let's try creating the same archive, but also extracting one at the same time:

 

Ah-ha! Now we're on to something, the SLC and Intel MLC drives are both around 30% faster than the OCZ Core. Let's try creating the same archive but extracting a much larger one:

  Creating 200MB Archive Extracting 5GB Archive Number of Pauses
SuperTalent (JMicron, MLC) 83 seconds 573 seconds lots
Silicon Power (JMicron, MLC) 128 seconds 632 seconds tons
OCZ Core (JMicron, MLC) 60 seconds 222.7 seconds 20
OCZ (Samsung, SLC) 42 seconds 94.7 seconds 0
Intel X25-M (Intel, MLC) 42 seconds 113.7 seconds 0
Seagate Momentus 7200.2 72 seconds 260.6 seconds 0
Western Digital VelociRaptor 46 seconds 90.9 seconds 0

 

You'll notice a new column called number of pauses; this column is the number of times all disk activity ceased on the system, causing the whole machine to stutter for a moment. You'll also notice that there are zeros in this column, unless the drive uses the JMicron controller. Also note the randomness of the problem, the OCZ, SuperTalent and Silicon Power drives all use the same hardware yet I saw tremendous variations between runs. This is a manually timed test but the rest of the drives didn't vary nearly as much.

It's also important to note that while the Seagate notebook drive performed similarly to the Core, it didn't suffer from the pauses. What this helps illustrate is the nature of the problem, it's very bursty - you get a period of very high performance followed by an abrupt stop. The abrupt stops, as we now know, are these 0 - 2 second write latencies where everything in the system is completely starved of data until the write is complete.


Poor hungry CPU, it just wants to eat. Comic by Laura of www.laurascomics.com

From the CPU's perspective, it expects new data on a nanosecond scale, waiting a full second for anything is deadly for performance.

Another way of quantifying the impact is looking at how long it takes to launch an application when we're in this high-latency write period. I tried extracting the same 5GB archive and launching PowerPoint 2007 or Photoshop CS3 (not at the same time).

  Launching PowerPoint 2007 While Extracting 5GB Launching Photoshop CS3 While Extracting 5GB
OCZ Core (JMicron, MLC) 8.5 seconds 24.3 seconds
OCZ (Samsung, SLC) 2.8 seconds 9.3 seconds
Intel X25-M (Intel, MLC) 3.85 seconds 10.5 seconds
Seagate Momentus 7200.2 21.3 seconds 46.5 seconds
Western Digital VelociRaptor 8 seconds 23.5 seconds

 

All of the drives took longer to launch the applications, but while the SLC and Intel MLC drives still performed in a league of their own, the MLC drives behaved like conventional hard drives. Try running an application while your disk is busy doing something else, or better yet, try running a couple - they take forever. SSDs fix that problem, or at least they're supposed to. These MLC drives don't, at least not always; thankfully the SLC drives and more importantly, the Intel MLC drive don't exhibit this problem.

Delving Deeper A Lack of DRAM or a Lack of Cache?
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  • bharatwaja - Tuesday, September 09, 2008 - link

    This is by far the best article I have ever read about SSDs... Anand you ROCK!!! and EVERYONE at ANANDTECH ROCKS!....

    Great article... Thank you........ you just saved me from spending $99 on a pretty much useless SSD.
    [Takes a printout of Anand to worship]
    Reply
  • hyperdoggy - Tuesday, September 09, 2008 - link

    I noticed that ocz have released core v2 series of their ssd. It seems to come in a different size configurations than its 1st gen product, can you confirm if this is based on the same controller as its 1st gen product Anand?

    Also, i would love to see some ssd raid action since ssd does not lose its data when the array fails. I'm more interested to see if there is other limiting factor when you raid with such fast ssds, such as the motherboard chipset itself. If raiding two of those cheap $99 core 32gig ssd helps to reduce the write bug, it might be worthwhile buy, which was something i was thinking of doing till i read the review here.

    And might i say, great review indeed Aanad.
    Reply
  • bytekeeper - Tuesday, September 09, 2008 - link

    Hi there. There is a discussion in the OCZ support forum about
    the test results published in this article and the OCZ support
    staff is thinking that you've got a faulty drive. Check here:

    http://www.ocztechnologyforum.com/forum/showthread...">http://www.ocztechnologyforum.com/forum/showthread...

    Is there any chance you can re run the test with another
    Core drive or Supertalent/Patriot JMicron JMF602 victims?

    Thanks.
    Reply
  • Gary Key - Wednesday, September 10, 2008 - link

    I posted results with a newly arrived Core drive straight off the shelf from Newegg in that thread. No changes to our initial results, although I will try a different controller later this week. Reply
  • Anand Lal Shimpi - Tuesday, September 09, 2008 - link

    In total I have four drives based on the JMF602 controller: one from OCZ, SuperTalent, Patriot and Silicon Power.

    Of the drives, the OCZ Core is the oldest. If you look at page 9 in the article I've got a table that has the SuperTalent, Silicon Power and OCZ Core drives in it. The Silicon Power and SuperTalent drive both perform worse than the OCZ.

    The situation gets more interesting if you look at the Iometer results for the drives, which I didn't publish in great depth but I did run internally. Average write latency goes down tremendously on the SuperTalent drive, but max latency more than doubled. I suspect that the SuperTalent drive may use a newer version of the JMF602, but the result is a reduction in real world performance - at least in the test cases I ran.

    The inability to complete an OS install also applies to other drives. As I mentioned in the article I had the same problem with the SuperTalent MLC drive in OS X.

    While there are undoubtedly ways of attempting to lessen the impact of the JMF602's poor design, I believe only a new controller will actually completely address these problems.

    Take care,
    Anand
    Reply
  • yottabit - Tuesday, September 09, 2008 - link

    This is why I love your website. Lots of your articles are so in-depth they make me think I'm reading some grad school journal that I should be paying money for.

    I actually first saw the Intel SSD article on TomsHardware, but didn't even bother to read it because I imagined it was going to say something like "OMG INTEL SSD ROX LOLZ SO MUCH FASTER THAN OTHER HDS"

    I come here expecting to get a detailed analaysis, and that's always what you provide! Thank you so much.

    My only gripe is you seem to have skipped a very basic test- dragging and dropping large files! You combine extracting files with other tests but you don't have any basic drag + drop tests I saw.

    This rocks for the computer industry though. I personally couldn't believe so many people were buying the existing SSDs. This new Intel stuff looks like something that would actually make an improvement without compromises. I could certainly live with the capacity, I'm still running a 36GB raptor for my boot drive. Hah.


    Reply
  • Dariusbird - Tuesday, September 09, 2008 - link

    I'm proud to be working for the company producing these IC's. Nice work on the article. Reply
  • therealnickdanger - Tuesday, September 09, 2008 - link

    It would be very nice to see where on all these charts the best 5400RPM 2.5" SATA drive would sit. Most laptop users have 5400RPM drives, so this would be MOST EXCELLENT to see the benefits of all these drives in comparison - especially the now "crappy" JM-based MLC drives. Reply
  • johncl - Tuesday, September 09, 2008 - link

    I must congratulate Intel for adressing the issues with MLC and creating a brilliant product. Also thanks to the author of this article to point to the problem of MLC that seems to go by unnoticed by so many benchmark review sites.

    The initial price from intel is suggested retail price so I guess in a short while this should come down a bit, as its a bit over the top. As the author says, at around $400 this is a no-brainer for an enthusiast considering the improvement you will experience on your system. This is for me the most important advancement in computer technology in the last years and we are just starting to see the advantages of it. Besides the person sitting behind the keyboard, the slowest thing in your computer is the harddisk. You can swap CPUs and GPUs to your hearts desire, but eventually, percieved performance of a computer often boils down to how fast you get data in and out of system memory. SSDs will fix this technological void we have had for all these years with mechanical disks.

    In general its about time we get rid of all mechanical parts in a computer, including fans. We need good cooling solutions built into our systems that rely on other means than rotating motors. If it means to stop the CPU speed race, then by all means do that, lets try to get todays performance but passively cooled. The SSD will walk hand in hand with this new trend in computing so we can get truly silent workstations. Amen to SSDs!
    Reply
  • Gastrian - Tuesday, September 09, 2008 - link

    I'm looking into creating a small multimedia PC where by I'll be archiving all my DVDs to DivX and running them through the PC instead of a DVD Player.

    Would I see any benefits in performance and acoustics (I don't want any noise from the PC interfering with my viewing) by having the OS on the Intel MLC SSD while storing the movies on a mechanical HDD?

    Essentially I want to be able to sit down and browse my movies then pick one and watch it without having to worry about loading/transfer times and noise levels.
    Reply

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