USB drive too slow for ReadyBoost

As I'm sure you're aware, Windows Vista introduced a feature called ReadyBoost which allows the operating system to make use of storage space on a USB drive or SD card to extend the available system memory. So if you have, for example, a 1GB USB drive handy you can plug it into your system and get a corresponding performance boost.

Now the problem with this is that all USB drives / SD cards aren't created equal and some may be too slow to be usable. If you do a quick search of the internet you'll find lists of compatible devices but I thought it worth mentioning something else you can try, mainly because I just tried it and managed to get over the "this device does not have the required performance characteristics" message. Simply try reformatting it using a different option (ie by right-clicking on the drive in Explorer and selecting "Format..."). Sometimes it seems to like you choosing NTFS as the file system, sometimes FAT32. And you can try playing around with the allocation unit size too.

For the 1GB drive I have just plugged into my machine FAT32 and 4096 bytes of allocation size did the trick. But it took a few attempts with different format settings to get it to work. So is my machine significantly faster? I''ll get back to you on that, at the moment I haven't noticed.

Alternatively, and if you're desperate, Windows Vista magazine has a slightly more radical approach that involves playing around with the registry. But be warned that a hack like this might not actually result in a faster system...

Comments (6)

  1. timts says:

    i dont quite understand the concept, as usb drive/ sd card is typically a lot slower than modern hard drives, how could that be a boost?

  2. Ian Moulster says:


    I oversimplified slightly: ReadyBoost is used as a cache for things that would otherwise come off of disks such as frequently used data, memory pages, ec.

    USB/SD cards are typically quicker than hard drives for small, random reads because of the seek times. Hard drives are much quicker though for large sequential operations. As ReadyBoost uses the USB/SD for small random reads only it outperforms hard drives.

  3. Richard Brown says:

    So in essence, what you’re saying is that you’ve tried various formatting options on a 1GB USB stick in order to get the best performance and having done so, you’ve no idea if its any faster than before?

    Genius. I think you should have a few days off after such a sterling effort.

  4. Ian Moulster says:

    Hmmm isn’t quite what I said. The world didn’t instantly become a better place, no. But ReadyBoost does absolutely improve performance so it’s worth persevering with it. At least, that was my take and what I was trying to do is let people know that if the first response they get is "your USB drive isn’t fast enough" they shouldn’t give up straight away.

    I may just take those few days off anyhow, thanks.

  5. fkautz says:

    Using FAT32 would actually slow it down substantially. The reason is that FAT32 is a linked-list based file system. Furthermore, if I remember correctly, FAT32 stores directory entries in an array.

    NTFS is implemented using a B+ tree, giving it faster lookups. In addition, once you locate a file, NTFS is able to jump to later parts of a file without traversing earlier ones.

    So, if you are working with large files or large file systems, you are much better going with NTFS over FAT based file systems. I would imagine this applies to ReadyBoost as well.

    p.s. timts: Writing to a flash drive is slow, but reading is generally quick. Some of the high end flash drives can read about 30MB/s. While this isn’t as fast as a hard drive, you need to remember that hard drives need to seek before they can write. On average, this takes half a turn of the platter. This usually takes 5-10 milliseconds depending on the quality of the drive. Flash drives that are supported by ReadyBoost are supposed to have an access time of 1ms or less (This is possible because flash drives are typically a collection of NAND gates which are randomly accessible).

    The result is that small data that has been swapped out of main memory into a flash drive is much more efficient than small data swapped to a hard disk if you need to access that data again.

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