A Lack of DRAM or a Lack of Cache?

The high latency random write issue is annoying enough that it'd force me not to recommend any of the non-Intel MLC drives on the market today, regardless of how attractive their pricing may be. High performance with caveats isn't exactly high performance to me.


Intel's controller (left) + DRAM (right)

That being said, the root of the problem is still unknown. My first thought was that it was because the MLC drives had no DRAM buffer, and if you'll notice, Intel's MLC drive does have a DRAM buffer. I asked Intel about this and it turns out that the DRAM on the Intel drive isn't used for user data because of the risk of data loss, instead it is used as memory by the Intel SATA/flash controller for deciding exactly where to write data (I'm assuming for the wear leveling/reliability algorithms). Despite the presence of the external DRAM, both the Intel controller and the JMicron rely on internal buffers to cache accesses to the SSD.

Finding good data on the JMicron JMF602 controller is nearly impossible, but from what I've heard it's got 16KB of on-chip memory for read/write requests. By comparison, Intel's controller has a 256KB SRAM on-die. And I'm going to go out on a limb and assume that given Intel's experience with CPU caches, that its SRAM implementation is probably very well done.

With the JMicron based solutions, if you try and write too much to the drive (and trust me, it won’t take a lot) and the buffers get full, the controller tells the system that it’s not ready to write more data and you get a pause.

When you cause the JM602’s internal buffer to overflow, your system runs in bullet-time. Applications take much longer to launch and close, windows take longer to appear, and there are distinct pauses in anything you want to do that involves the disk. Want to send an IM? Well, that writes to an IM log - you can expect a pause before you can send your IM. Loading webpages is the worst, reading from and writing to the cache wreaks havoc on these cacheless MLC drives. Just for kicks I tried loading AnandTech while I was extracting a 5GB file on the SuperTalent 60GB MLC, it took over 10 seconds for the website to load. Once the JM602 was free to fulfill the read request, the website just popped up - but until then it was like my DNS was failing. It’s a lot like what happens to your notebook if you try and do too much, the disk quickly becomes a bottleneck.

Thankfully, as we've already seen, this problem is only limited to JMF602 based MLC drives. The SLC drives and the Intel MLC are totally fine, so while I'll include these problematic MLC drives in today's comparison, let me state now that I would not purchase one.

JMicron's roadmap shows a new controller next year with an integrated ARM core as well as support for external DRAM, which could alleviate these problems, but until now the controller, and drives based on it, aren't worth it. You get a much better overall experience out of a conventional mechanical disk drive, and much better performance from the Intel SSD or any of the SLC solutions on the market.

The Test

CPU: Intel Core 2 Quad Q9450 (2.66GHz)
Motherboard: Intel DG45ID
Chipset: Intel G45
Chipset Drivers: Intel 8.1.1.1010 (Intel)
Memory: Corsair XMS2-8500 1066
Video Card: VisionTek Radeon HD 4850
OS: Windows Vista Ultimate 32-bit

 

The Generic MLC SSD Problem in the Real World Overall System Performance with SYSMark 2007
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  • Donkey2008 - Monday, September 08, 2008 - link


    Starting sentences with a conjunction is acceptable, but it is considered bad prose. You are giving everyone a headache. Go take your ritalin.
    Reply
  • ggordonliddy - Monday, September 08, 2008 - link

    As you stated, my English usage was correct.

    And I'm not the one writing the article; the burden is much greater on the people who are being PAID to write, as it should be. They are setting the example for others.
    Reply
  • mindless1 - Thursday, September 11, 2008 - link

    As a paying customer I urge you to ask for a refund. Reply
  • Jingato - Monday, September 08, 2008 - link

    What kind of loser gives a f*** about improper use of commas? This aint a novel, it's a friggin tech site.

    lol get a life.
    Reply
  • ggordonliddy - Monday, September 08, 2008 - link

    You are just making it clear that you do not have a firm grasp of English. You are afraid of those who criticize poor grammar, because you know that you yourself will be exposed for the fraudulent pustule that lies beneath your slimy veneer.

    I have a life. I'm just sick of illiterate authors. Just because it is a tech site is no excuse for extremely poor writing skills. I'm talking about skills that should be completely mastered before being allowed to graduate from elementary school.
    Reply
  • Jingato - Tuesday, September 09, 2008 - link

    No, I just don't give a f***.....there's a difference.

    I think you're being way too over critical. Maybe it's you OCD kicking in. If those incorrect commas really bothered you THAT much, then you should seek professional help. Seriously, that's not normal.
    Reply
  • aeternitas - Thursday, September 11, 2008 - link

    If you dont give a ****, then shut the hell up. Reply
  • Gannon - Tuesday, September 09, 2008 - link

    Anand's editors should get this:

    http://www.whitesmoke.com/landing_flash/free_hotfo...">http://www.whitesmoke.com/landing_flash...otforwor...

    I've used it, it is not currently on this machine but what you do is you press "F2" and it checks your grammar and makes suggestings and points out errors, etc.
    Reply
  • DerekWilson - Tuesday, September 09, 2008 - link

    From your comment:

    "You are afraid of those who criticize poor grammar, because you know that you yourself will be exposed for the fraudulent pustule that lies beneath your slimy veneer."

    "... that you yourself will be exposed ..." should, in fact, be properly punctuated with commas like so: "... that you, yourself, will be exposed ..."

    I agree that grammar is important. But you have to admit that screwing up on comma usage while pointing out someone screwing up on comma usage is funny.

    ...

    Also, while it isn't an excuse, the last two days of work on this article were sleepless ... Anand wanted to get it up much sooner, and sometimes we have to make the decision to get the article out quickly rather than to send it through our managing editor.

    We do always appreciate people pointing out spelling and grammar errors in our articles. We never want to over shadow the content with other issues.
    Reply
  • ggordonliddy - Tuesday, September 09, 2008 - link

    > "... that you yourself will be exposed ..." should,
    > in fact, be properly punctuated with commas like so:
    > "... that you, yourself, will be exposed ..."
    >
    > I agree that grammar is important. But you have to admit
    > that screwing up on comma usage while pointing out someone
    > screwing up on comma usage is funny.


    Wrong. A comma is not required between "you yourself." See http://www.selfknowledge.com/109331.htm">http://www.selfknowledge.com/109331.htm and other examples.

    I am a bit sorry for being so abrasive in my original post though. Run-on sentences just drive me nuts.
    Reply

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