RAM drive on a USB pen drive?

Discussion in 'Mac Accessories' started by Dreamkatcha, Dec 9, 2006.

  1. Dreamkatcha macrumors regular


    Mar 17, 2003
    Manchester, England
    If you could do this it would really speed up laptops and Mac Minis with slow hard drives. Does anyone know if it's already been done?

    I found some patent info relating to this, but no software.
  2. FireArse macrumors 6502a

    Oct 29, 2004
    RAM drives

    I have been able to partition my RAM into mounted drives, allowing for fast data access - I cannot see why the other way around couldn't happen. So let me get this straight - you wanna plug in a 2GB USB stick, and tell the mac to use it as RAM?

    Flash memory is quite a bit slower than conventional RAM, but I'll have look...

  3. Shadow macrumors 68000


    Feb 17, 2006
    Keele, United Kingdom
    Vista has this, but it sucks. Literally *no* performance improvement.
  4. Dreamkatcha thread starter macrumors regular


    Mar 17, 2003
    Manchester, England
    Yep, that's the idea. These days everyone seems to have spare USB sticks lying around gathering dust. Wouldn't it be great if you could get a performance boost just by plugging one into your USB slot.

    Chris, I think that's what Leo Laporte was referring to when he mentioned it on TWiT. That's where I heard about it. I suppose the gain all depends on the specs of the test system. Once these hard drives with massive RAM caches built in are in common use, a hack like this will be redundant.
  5. orangezorki macrumors 6502a

    Aug 30, 2006
    I think you might be getting a bit confused. A RAM drive is using a portion of your RAM as a disk, not any other type of disk - optical, HD, flash or otherwise. What it sounds like your looking for is to improve the performance for writing temp files etc by using something faster than the laptop HD. Your best bet for this is an external 7200rpm, 3.5" HD, connected by firewire. Flash memory is not RAM, and is actually usually much slower than a HD, except for the very expensive professional grade flash memory cards.

  6. CanadaRAM macrumors G5


    Oct 11, 2004
    On the Left Coast - Victoria BC Canada
    Unclear on the concepts, mate.

    #1: USB is slower than real RAM and slower than hard dxrives. USB 2.0 Theoretical 480 Mbs vs. Theoretical 3200 - 8000+ Mbs for RAM. Plus USB imposes a CPU load which is undesirable. Of course, real life USB 2.0 throughput is far lower than the theoretical...

    #2: Flash memory in keychain drives is slow - the fastest ones are in the 15 - 21 Mbs read time and considerably slower for writes.

    #3: Because most affordable flash memory has to be erased in a block before being written to (that is, it does not support direct overwriting), Flash memory is REALLY slow for many, small writes... way slower than a fixed hard drive.

    #4: Flash memory has a finite number of times that it can be written to before it dies. Not an issue for a camera card, which you'll write maybe once a day for a few years for a few thousand writes over its lifetime. But, worst case, as a scratch disk, the 'drive' will be written to thousands of times per hour. Sudden Flash Death predicted.

    FireA -- the 'other way around -- using a hard drive as an extension of ram -- happens every minute of the day on your Mac, it's called Virtual Memory. OSX make extensive use of swap files on the hard drive, as does every modern operating system. But hard drives are way slower than RAM, which is why when you have too little RAM, and the machine is forced to use hard drive space for active memory, the machine slows down considerably.

    Putting VM / swap space on a USB flash memory device would be a terrrrrible idea.

    Using a different, faster kind of Flash memory from that which is used in consumer flash devices, it is potentially possible to improve performance, particularly hard drive performance - but then, hard drives already have 8 - 16 Mb of SDRAM on them for caching.

    The problem with using Flash memory for RAM extension is that the Flash would have to be on the main memory buss, or something just as fast. If you put it on the SATA buss, or the PCI-e buss, then you're cutting the bandwidth down and increasing overhead. OK for hard drive caching, maybe, which is why we'll see hard drives coming in the future with big caches, but not for RAM. Then, if you are going to attach something to the Memory buss, why wouldn't you just install DDR2 memory, which is a LOT cheaper than any type of Flash memory that would be fast enough and survive repeated read/writes?
  7. Dreamkatcha thread starter macrumors regular


    Mar 17, 2003
    Manchester, England
    Hmm, this is beginning to sound like a non-starter. Luckily I wasn't looking to solve a specific problem, it was more of a curiosity than anything.

    Yes, you're right, orangezorki. What I was interested in knowing was if it's possible to create a kind of swap file on a USB drive. So it looks like it could be done, but there would be no point. I wonder why Leo was getting so excited then.
  8. Sesshi macrumors G3


    Jun 3, 2006
    One Nation Under Gordon
    You mean the new flash-as-VM feature in Vista?

    Anyone trashing the feature's performance using random pen drives is a non-starter as a knowledgeable source for part of the reason that CanadaRAM mentioned.

    Try this source for a start about drives which take advantage of the new Vista ability.

    If it works out as a potentially high-performance feature under OS X as well I suppose Apple will adopt it too. No reason to assume why they won't really unless there's something very Vista specific about it.

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