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geofftech

USB hdd average transfer rate

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I've found that all usb hard drives that I've placed in USB enclouses according to HD Tach seem to max out at 33MB's. This is strange when I know USB has a theoretical max of 60MB's. One of the drives tested was a Seagate Momentus 7200.1 910021AS SATA drive. Any ideas.

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Remember, for as long as the HDD is transferring faster than 60MB/s, the overall rate is stuck at 60MB/s, and after that, the transfer rate goes down (goes from being limited by the USB bus to being limited by the hard drive.)

However the average should be higher than 33MB/s, given that most HDDs now can manage rates over 60MB/s for quite some time.

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USB implementations in computers and external drives aren't perfect; typically one of these is the bottleneck. Also, I've heard that the USB protocol has some inefficiencies, so 40 MB/s is closer to the maximum STR than 60 MB/s.

If it makes you feel better... my USB/drive give me a max around 27 MB/s, even with a drive that averages > 60 MB/s and has a minimum > 40 MB/s.

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I have a Vantec eSATA external case and when I connect my Hitachi 160GB SATA II single platter 7K160 HDD to it and run it off the USB2 port it gives me 33MB/s but when I connect the same HDD as eSATA I get 62MB/s

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USB sucks for fast mass storage. It's that simple.

If you want to get closer to your max hard drive capability, use eSATA or FireWire 800 (aka 1394b.) eSATA is the best (since it is the exact same bus as used internally,) but if you can't do that for whatever reason, go for FireWire 800.

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USB sucks for fast mass storage. It's that simple.

If you want to get closer to your max hard drive capability, use eSATA or FireWire 800 (aka 1394b.) eSATA is the best (since it is the exact same bus as used internally,) but if you can't do that for whatever reason, go for FireWire 800.

yeah I got a Bytecc BT-280SATA COMBO enlcosure to go with the Seagate and use the eSATA port on my desktop. Just wish I had faster speeds elsewhere. Thanks for your replies.

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In reality, the maximum transfer speed for USB2.0 is around 35 MB/s. Even FW400 gives better results...

That's just so.

But yes, as already mentioned here above, you must use eSATA or FW800 or LAN1G to get almost full speed out of today's 3.5" drives.

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My observation over the years is that USB enclosures like the Vantec which use JMicron 2033x controllers routinely averaged between 30-33MB/s on large transfers (similar performance to older FW400 controllers) , those based on the Prolific 2507/3507 and Genesys Logic GL-81x average between 22-24MB/s depending on firmware level. Reliable but relatively slow Cypress CY7C683XX solutions would only do around 19-21MB/s on average.

eSATA plus USB2.0 as secondary interface is the way to go.

Edited by tracker

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