Expected USB 2 Transfer Rates?

[Will Rickards]

What transfer rates should I expect for a hard drive in an external enclosure hooked up via USB 2? I'm getting something like 24MB/s and wondering if that is good or slow or what.

Here are some hdtach screenshots
Quick Test
Long Test

 

[timwhit]

What kind of hard disk?

 

[Handruin]

I'll try running a similar test on my USB 2 external when I get home to see if I get similar results.

 

[Will Rickards]

It is a maxtor 120GB DiamondMax Plus 9 120GB
Storage Review Link

 

[ddrueding]

Considering my USB drives just got delivered on the other side of the country, it'll take a while for me to run the tests

 

[Stereodude]

That's in the ballpark depending on the chipset used in the enclosure...

 

[Mercutio]

24MBps has been known as a real world limit for USB2 bridge chips for some time. I know specs would indicate better performance, but it just isn't there.

This limitation is a very good reason to look at Firewire products.

ddrueding, your drives are only halfway across the country.
And even though they may have been delivered I won't be able to pick 'em up 'til Friday.

 

[Buck]

This limitation is a very good reason to look at Firewire products.

Yup. Particularly FireWire 800. This article from Xbit shows some nice data regarding interface speed differences.

 

[Will Rickards]

So while USB 2 might be able to do 480Mb/s 60MB/s via the spec and in real life maybe 55 MB/s, the parallel ATA to USB 2 bridge chip is only letting 24MB/s through? Or is USB 2 not even capable of reaching 55MB/s?

Seems via this wikipedia link most usb 2 devices only are capable of half the 60MB/s which is a max of around 30MB/s.
http://en.wikipedia.org/wiki/USB

So I guess 24 isn't bad. At home I was getting 26MB/s.

 

[Buck]

So while USB 2 might be able to do 480Mb/s 60MB/s via the spec and in real life maybe 55 MB/s, the parallel ATA to USB 2 bridge chip is only letting 24MB/s through? Or is USB 2 not even capable of reaching 55MB/s?

Seems via this wikipedia link most usb 2 devices only are capable of half the 60MB/s which is a max of around 30MB/s.
http://en.wikipedia.org/wiki/USB

So I guess 24 isn't bad. At home I was getting 26MB/s.

I would say the reduced rate of USB 2.0 is the result of hardware/firmware implementation and drivers.

 

[Handruin]

I ran my tests using the same tool and I'm getting a bit better transfer rates than you over USB 2.0. I'm using a Vantec USB 2.0 + eSATA external enclosure with a 400GB Samsung drive. The tests were run with eSATA disconnected of course.

 

[Will Rickards]

I'll have to look into that enclosure as this one's fan is way too loud.
How noisy are those? Near silent? There seems to be so much air space around the drive in mine I don't even know why they need a fan?

 

[Stereodude]

I won't buy USB 3.5" HD enclosures that use a fan. I get fanless aluminum ones with Cypress chipsets. Call me picky I guess...

 

[Handruin]

My Vantec is fanless (and Aluminum), so it is very quiet. This is the unit I bought:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817145167

With my Samsung 400GB, I've had it running for hours on end with no real heat issues. I don't run it 24x7 though, I think that might be too much for it.

The eSATA is a nice bonus. I use that most of the time on my home machine (Vantec provides the L bracket to make it external). I don't know what USB controller is in it, but I can bust it open to find out.

 

[Pradeep]

I get about 35MB/sec out of the Oxford 911 based chipsets (Firewire). I also have an FW800 enclosure, never benched it to see, but I think it can do around 55MB/sec.