An acceptable transfer speed for external HDD?

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BlackIce72

n00b
Joined
Dec 11, 2005
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First off I am pretty much a computer noob. But that doesn't mean you need to dumb down the advice, because I'll pick up on it pretty quickly.

I just picked up a 160gb WD MyBook at bestbuy for $80. In retrospect, I probably should have just gotten an internal HDD and an external box for it. But that's not the point.

I also picked up a USB2.0 PCI card because my desktop doesn't have USB 2 ports. Anyway, I hooked up the HD and it just seemed to be transferring very slowly-- perhaps 8mb/s. The guy at CompUSA said it would transfer at about .5gb/s.

So what's more of an expected and acceptable speed? Is there something wrong with the USB2.0 port, the HD, or me? Or, is 8mb/sec just fine.

My computer is far from impressive, and is very much dated by some standards.

AMD Athalon64 3000+, 2GHz, 1 gb RAM.

Any and all advice is appreciated. Let me know if you need more info.
 
Once again, half-knowledge strikes: The BB employee probably heard that USB 2.0 transfers data at up to 480Mbps (megabit, not megabyte!) and assumed that this was applicable to harddrives. Unfortunately, the way in which people use mass storage devices requires not only that data sent will arrive and be stored, but also that the stored data matches the sent data. The maximum USB 2 speed is only achievable with isochronous frames, which do not guarantee delivery or data integrity. This works fine for webcams etc, where it does not matter when a couple of pixels are missing, but not for HDDs.

HDDs are limited to Bulk/ Interrupt transfers which happen much slower so that the real-world transfer rate of a good USB enclosure is somewhere in the 20-30 MB/s region. Given that, if your MyBook transfers at 8MB/s I would suspect that it may come with a poor chipset, since that speed is too fast for USB 1.1. It may also be that you have a driver problem.
 
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