Dual Channel Flash Drives

With flash drives, the fewer chips you use, the smaller your device can be and the cheaper it can be as well. It is almost always cheaper for a manufacturer to use one 4Gbit flash device than to use two 2Gbit devices, so as long as there is a high enough density available, you would expect manufacturers to always opt for a single chip flash solution (at least for the memory). Lately, however, some controller manufacturers have offered "dual channel" controllers that allow you to read from/write to multiple flash devices simultaneously; think of it like RAID-0 for flash drives.


A multi-channel USB flash drive; note the presence of two flash devices to the right of the OTi controller.

Most USB flash controllers feature a single 8-bit wide interface to their flash memory, but a dual channel controller features a 16-bit wide interface and can read from/write to two flash devices at a time. Most NAND flash devices used in these drives have a 2112 byte page size, so whenever data is written, it is done in 2112 byte chunks. For a dual-channel device, all data reads and writes are effectively striped across the two memory devices, much like in a RAID-0 array.

The performance boost for a dual channel drive over a single channel drive depends a lot on the type of flash used as well as the controller itself. In many cases, however, a dual channel drive can be up to 2x as fast as a single channel drive.

Most physically larger drives that are branded as high performance drives are dual channel solutions, even if they aren't marketed as such. The cheaper drives end up being single chip/single channel, and of course, the small form factor drives end up being single chip/single channel as well.

The Performance Equation USB Flash Drive Security
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  • BJL - Monday, October 16, 2006 - link

    Do the read and write speeds change for the 1gb and above models? Would I get the same performance, or should I stick with the 512mb? Reply
  • NeoZGeo - Monday, October 17, 2005 - link

    what kinf of benchmark are you guys using? How come some of those drive write speed is sooooo low!? Like Trenscent, OCZ Rally, i've seen some reviews out there which says other wise. Reply
  • NeoZGeo - Monday, October 17, 2005 - link

    here's the review by tom's

    if you look at the trenscend jet flash, it actually has the highest write speed average out at 23.3 mb/s vs anandtech's 8.7 mb/s !? what the hell?
    Reply
  • NeoZGeo - Monday, October 17, 2005 - link

    haha oops, forgot about the link :D

    http://www.tomshardware.com/storage/20050520/usb_f...">linky
    Reply
  • quanta - Wednesday, December 07, 2005 - link

    It looked like Tom's test is testing the write speed between USB host and flash drive's controller's memory buffer, instead of actual write speed, which can only be verify by doing a read after writing is completed. There are also reports that http://www.auphanonline.com/articles/view.php?arti...">cluster size may affect the write access behaviour. BTW, Tom's http://www.tomshardware.com/2005/08/10/two_fast_an...">later review has simultaneous reads and writes benchmark, which slows Memina Rocket to a halt. Reply
  • quanta - Wednesday, December 07, 2005 - link

    In addition, even when using buffered write in SiSoft Sandra, it is extremely unlikely that Transcend Jetflash 110 can write anywhere near 23.3MB/s. http://www.oc.com.tw/article/0510/readparticle.asp...">This benchmark shows that when doing random write with Kingston DataTraveler ELITE, write speed dropped more than a half compared to sequential write. Reply
  • TrueWisdom - Wednesday, October 12, 2005 - link

    I'm the in-house support for a university building and I've had absolutely horrible luck with Lexar drives. Lexar often fails to detect entirely on somewhat older machines (the Latitude C840, for example) and has also displayed a relatively high failure rate for me. I don't have any positive or negative impressions of Kingston drives, so I can't say anything there, but I will say that I've had by far the best luck with Sandisk drives. I've never had one fail on me, and I've seen them go through wash cycles, get run over by a car, and get left out in the rain. Compatibility has been universal as well. They may not be the fastest drives but they really are the only ones I've ever trusted. Reply
  • pendrivethis - Friday, October 07, 2005 - link

    i work for a flash memory controller maker and in all honesty the most meaningful performance test is random write. and no one really advertise that since sequential read speeds seem much more appealing and marketable. i can get a dual-channel & interleaving enabled usb 2.0 pen drive with micron or samsung nand-type flash to go up to 34mB/s in sequential read, but the engineer who designed this still tells me that he'd rather use and-type flash from renesas (formerly hitachi) since and flash has a better random write than nand flash.

    and knowing what i know, if you use your pen drive very often, and i suspect some of you may be in that boat, i'd check out some of the burn-in testing results especially since companies are not entirely using only samsung nand flash. certain new flash whether nand-type or ag-and-type and even some high-density samsung flash seem to be displaying a need for extra care in ecc. data-verify errors are fatal, especially if it's the only copy you got...

    anand, perhaps a little visit to some of the design houses for these controllers the next time when you're in taiwan is in order. computex is only 9 months away.
    Reply
  • sprockkets - Thursday, October 06, 2005 - link

    Although not reviewed here, I got the A Data key from newegg.com simply because they say it works with Linux on the package. I know any key will, but they are the only ones to have the guts to say it. Thanks for admitting Linux exists. Lifetime warranty too. Reply
  • jgh - Wednesday, October 05, 2005 - link

    here is a link for another link, to an app that can make many (but probably not all) usb drives bootable and a couple of other hints/tips.

    http://www.oreillynet.com/pub/wlg/5735">link

    O.T. - for some reason i get a message that says i do not have permission to access this forum when i tried to create a new login with my e-mail address. did i get banned or something? i have only posted once (it was about the gta:lcs website). i also cannot log in with the origianl user name and password.

    p.s. - it is o.k. to post links like this right?
    Reply

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