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USB Flash Drives or Pen Drives for Vista

While this article refers to Windows Vista, the information is applicable to any OS that supports USB flash drives, and it's also applicable to any other USB device that claims to be "USB 2 compliant".

Caveat Emptor

Not all 'Hi-Speed" USB flash drives are high speed. unwary consumers can be caught out by misleading words or, as in most cases, completely missing information about the USB flash drive's read/write specifications.

If you don't have any information about a flash drive's read and write speeds then there is no way to know that you might be buying a painfully slow lemon until you get your shiny new pen drive home, plug it in to your PC and immediately go into catatonic shock when you see the blatant lack of performance. There are fast "Hi-Speed" flash drives and there are woefully slow "Hi-Speed" flash drives. This article tells you what you need to know so you don't get stuck with a next to useless, woefully slow "Hi-Speed" flash drive.

"USB 2.0 compliant" means exactly that; it does not mean "USB 2.0 capable" or "designed to USB specification revision 2.0". If the USB component is designed for USB 1.1 then it is automatically "USB 2.0 compliant", which does not mean that the USB component operates at USB 2.0 speeds. Read this article to help avoid being sold slow, out of date rubbish that you neither need nor want.


Windows Vista includes a feature called ReadyBoost, which is a cache that can be stored on high speed USB flash drives to increase Vista's performance. Not all 'Hi-Speed" USB flash drives are fast enough for Vista though; Vista's minimum specification for ReadyBoost-capable high-speed flash is 2.5 MB per second on 4KB random reads, and 1.75 MB per second on 512 KB random writes. That's megabytes per second, not megabits.

Misleading Advertising?

Most packaged flash drives have text emblazoned on them that says something along the lines of "2GB Hi-Speed USB 2.0 Flash Drive", but the packaging is utterly silent on the flash drive's actual access times. If the flash memory itself is not explicitly included in statements about high speed then the statements should be assumed to relate only to the speed of the USB interface and not to the access speed of the flash memory. At the end of the day, any USB device, even a slow one, is "Hi-Speed" when compared to a floppy disk, and any USB device is considered by manufacturers to be "Hi-Speed" if its interface works at USB 2.0 speeds, but that does not mean the flash memory of a USB pen drive is anything approaching high-speed.

A Case in Point

In amongst past advertising blurbs for the Lexar Firefly were superlative marketing phrases like "Ultra-Small Storage with Huge Personality", "More Than Just Good Looks", "Serious Power", "Great Features" and "Pick One to Meet Your Needs", was the statement, "Behind those cool colors lies the heart of all your information. The powerful, hi-speed USB JumpDrive FireFly..."

Lexar's newer advertising uses superlative phrases like "Cool design and flashy colors", "Ultra small, ultra portable", "Massive storage capacities" and "High-performance USB flash drive". The advertising even includes an in-your-face graphic that explicitly states, "Works with Windows Vista".

The Lexar JumpDrive FireFly is not "hi-speed" enough for Windows Vista. In fact, the Lexar JumpDrive FireFly's access speed is slower than a week of rainy Sundays. kadaitcha.cx knows this because kadaitha.cx got stuck with two of them. Taking almost two minutes to copy 150MB is not "hi-speed". A much older Lexar JumpDrive, a different model to the FireFly, does the very same copy of 150MB in under 25 seconds.

An older flash drive can have performance characteristics that are acceptable to Vista's ReadyBoost; the newer and higher-capacity Lexar FireFly does not; Vista will not use the Firefly as a ReadyBoost cache because the Firefly is not up to standard. This problem could not have been known about by reading any material available from the manufacturer. Indeed one could be forgiven for thinking that "Works with Windows Vista" might mean the drive is ReadyBoost compatible, but it means no such thing. The phrase "Works with Windows Vista" means exactly what it says; the drive will work under Vista, as a drive. You will note that there is no statement anywhere in the Lexar advertising for the FireFly about ReadyBoost; not a single word.

Lexar were kind enough to furnish proof that the above is true; they provide a JumpDrive comparison chart where all is revealed. The flash drives that are good enough for Vista all state "Enhanced for Windows ReadyBoost"; no such claim is made for the FireFly, though Lexar do claim that the drive is "Windows Vista compatible", which isn't the same as ReadyBoost compatible.

In short, if the packaging for the pen drive does not explicitly state that the drive is ReadyBoost compatible then you should assume it is not ReadyBoost compatible at all. You should apply that rule even if the package says "Works with Windows Vista".

So, is it misleading advertising? Technically, no. Marketing spin-doctors are relying on the assumption that 99% of the population are too stupid to work out the real meaning of the words used in their blurbs.

Other Alternatives

If you are purchasing a pen drive from a reputable store then insist that the sales representative agrees to let you return the drive if it turns out the drive cannot be used by ReadyBoost.
Rely on the shared experience of others who have been caught out; to do that, visit grantgibson.co.uk and choose any flash drive marked as being "ReadyBoost Compatible".
Caution: Avoid any entries with user comments that say things like, "at least I think it works", or "I believe this should work", or "I had to test it a few times but I think it eventually worked."

One More Caution - U3 Flash Drives

Flash drives that support U3 cannot be used as bootable devices while U3 is installed because U3 does not follow the standards for USB storage devices.
The U3 software sits inside a pseudo-CD-ROM drive within the flash drive. When you boot with U3 installed, the pseudo-CD-ROM is loaded first, and the data partition on the drive is only enabled after you have authenticated;
The presence of the pseudo-CD-ROM will cause your operating system to become horribly confused and it will not boot. kadaitcha.cx is not aware of a method to boot from a U3-enabled device without eliminating U3.


If you want to boot from a U3-enabled device, you will have to try the tools linked to above to eliminate U3, then find some other way of protecting your data. The Open Source TrueCrypt is highly recommended if you need data security.

Note: Reports indicate that the above tools are not always 100% successful so you might have to try both. If you still can't get rid of U3, try Google.