Is USB 3 Really Faster?

[rainwilds]

Transferring 50gigs of data from my external USB 3 hdd to my SATA RAID runs out a maximum of 100mbps. Shouldn't the transfer speed be around 200? I've ensured I have the settings enabled in BIOS for USB 3.

 

[compulsivebuilder]

Are you using megaBYTES / second? Or megaBITS / second? I generally use MB for megabyte and Mb for megabit (and mb for millibit - a quantum concept related to quarks).

You can't get a sustained transfer that's faster than the slowest link. In the past, USB2 was the slowest link, but USB3 is much faster.

If you are getting 100 megabytes/second, I'd guess that the limiting factor would be the drive in your external drive. They tend to be 5400rpm "green" drives, which aren't the fastest things around. The RAID should be able to deliver a higher rate, and so should the USB3 connection.

 

[rainwilds]

MegaBytes, megaBits all too confusing sometimes! Whatever the transfer rate shows in Explorer... I think it's megaBits.

Ahh, you could be right about the external drive though I think its a Samsung F4 (damn eco. drive) which is 7200rpm, but will have to check. What do you get for a transfer?

 

[pjmelect]

That transfer rate (assuming that you are talking about Mega BYTES) is still three times faster than USB2. The transfer rate shown in Explorer is in BYTES.
Assuming the hard drive can transfer data at a rate faster than 100 M/Bytes which depends on where about on the disk the data is stored the other limiting factor is the speed of the SATA to USB converter.

 

[sminlal]

The limitation is in the hard drive, not in the USB 3.0 connection. No current hard drive I'm aware of can transfer at 200 MByte/sec - the fastest ones top out at less than 150 MByte/sec, and those only achieve that speed when they're using the outermost (fastest) tracks. All drives transfer more slowly as the heads move toward the innermost tracks - the very innermost tracks are typically only half as fast.

USB 3 is indeed giving you a huge benefit, since you'd only be seeing around 35-40 MByte/sec if you were using USB 2.0.

 

[rainwilds]

That all makes sense. So I guess the marketing department of Lacie convince the un-informed by emphasizing you could get up too 600MB/s.

■The SATA 3 interface (which is what my RAID is on) has a maximum transfer rate 300 megabytes p/s.
■The Spinpoint F4 (in my Lacie external case) has a max speed according to test of around 95 megabytes p/s. The 100 I'm getting than is great.
■USB 3 has 625 megabytes top speed. Good luck reaching that on my drive!

Before you could get anywhere near USB 3 speeds you would first need an external SSD (maybe in RAID 0) interfaced on a SATA 6 connection!

While I'm at it, what's the point of Apple's Thunderbolt with up to 1250 MB/s? What device can utilize that speed?

 

[sminlal]

While I'm at it, what's the point of Apple's Thunderbolt with up to 1250 MB/s? What device can utilize that speed?

Thunderbolt is designed to handle video, which has extremely high bandwidths. For example a 2650 x 1600 display refreshing at 60Hz requires 2560 x 1600 x 3 (bytes/pixel) x 60 = ~740MByte/sec.

 

[pepe2907]

It's only if the video is uncompressed, which is never the case /except when delivered from your graphics card to the display/. Tipical speeds for high def video as shot by cameras /pro cameras/ is tipicaly between 50 and 150 MB/s. After that it's usualy compressed further...
A DVD - 2 hour - 4GB - you may calculate it

 

[sminlal]

It's only if the video is uncompressed, which is never the case /except when delivered from your graphics card to the display.

That's exactly my point, Thunderbolt is designed as a video display attachment bus (among other things) - in other words, as a replacement for a VGA, DVI or HDMI connection.

 

[mpavao81]

i myself am not really impressed with USB 3, I put a 2tb caviar black in a max5G external enclosure and transfered a 13GB file and averaged around 70MB/s took that same hard drive and put inside my computer on a Sata II interface and transfered the same file again and averaged 119MBs.

I wish I would have gotten a external enclosure that had esata instead of usb3. an average of 70MBs does not seem all that impressive.

 

[rainwilds]

Thunderbolt is designed to handle video, which has extremely high bandwidths. For example a 2650 x 1600 display refreshing at 60Hz requires 2560 x 1600 x 3 (bytes/pixel) x 60 = ~740MByte/sec.

So I guess that explains why you need two DVIs to run at 2560x1600; and a decent video card.

 

[pepe2907]

mpavao81 the direct SATA connection is more ...direct. USB how ever good it may be allways adds additional reformatting of data packages, buffering, sinchronisation... So it will allways be slower as the direct SATA connection. Plus USB 3 is just the standard. The hardware you realy utilize should more or less correspond to the requirements of the standard, but there are tollerances /especially when the standard is relatively new these tollerances are lose, do you remember first USB2 devices?/. And usualy the electronics, involved in this buffering-reformating thing even looks kind of junky

 

[sminlal]

So I guess that explains why you need two DVIs to run at 2560x1600; and a decent video card.

Yes, exactly. Although you don't need two cables - the DVI standard includes dual links within the same cable/connector - its a matter of whether the devices at each end support both links or not.

 

[rainwilds]

Yes, exactly. Although you don't need two cables - the DVI standard includes dual links within the same cable/connector - its a matter of whether the devices at each end support both links or not.

You learn something new everyday!