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Windows 7: USB3 - The performance mystery


24 Apr 2011   #1
whs
Microsoft MVP

Vista, Windows7, Mint Mate, Zorin, Windows 8
 
 
USB3 - The performance mystery

Since the availability of USB3 on the market, there has been a lot of guessing – and disappointments – regarding the performance of this new external attachment option. In this article I will try to clarify some facts that rule the speed of the various disk attachments.


Note1
Quote:
For simplicity reasons, I will use Megabytes (MB) as the discussion unit. I convert 1MB from 10Mb (Megabits). That is not quite exact, but that is close enough. One byte has 8 data bits and 1 control bit. In addition, there is control information when a file is written to disk.
Note2
Quote:
The data I use for this analysis is from my systems. Those are not absolute numbers. You may see different numbers on your system depending on your hardware configuration. If you run the Atto tests on your system, you will get your numbers and can compare.
Disk performance

It is important to understand what you can expect from your disk(s). Rotating disks will typically have Read/Write speeds between 60 and 100MB/sec, some are a bit faster. But this applies only if the blocks are rather large – 128KB or larger. If the blocks are small, e.g. 4KB as the Windows NT systems mostly use, the R/W speed will be significantly lower. 4KB is also the formatted blocksize on the current disk hardware.

If you want faster R/W speeds then you can choose an SSD. They provide speeds up to 350MB/sec for Reads and somewhat less for Writes.

The top dog in the disk speed race is a Revo drive which is configured as 4 way hardware Raid. They attach via PCI-E x4 and have R/W speeds around 500MB/sec and more (Example).

Attachment performance

USB2 can transfer data up to a maximum speed of 48MB/sec. That means that a fast disk or SSD cannot Read or Write at speeds at which it would be capable.

USB3 is a lot faster – it can transfer data at speeds up to 600MB/sec. However, there are no disks (rotating disks or SSDs) on the market at this time that can feed the attachment at that speed.

eSata is another option. It provides transfer capability up to 300MB/sec. That is ample for rotating disks and possibly a bit tight for top performing SSDs (if big blocksizes are used).

Firewire (IEEE 1394) is an external attachment method that comes in two versions – a 40MB/sec and an 80 MB/sec version.

PCI-E x4 is the attachment method for Revo drives. It can transfer data at speeds up to 1000MB/sec.

Measurements

I have measured USB2, USB3 and eSata on my systems. I use Atto because it seems to provide the most consistent results. But there are other measurement tools (e.g. HD Tune) that may provide slightly different numbers.

Test1 – here I use a 5400RPM disk running from USB2 and USB3









As you can see, USB3 is more than 4 times faster for large blocks and about 3 times faster for 4K blocks.

Test2 – here I use a 7200RPM disk attached to eSata






This is faster than USB3. The 4K times are twice as fast. But consider that this was a slightly faster disk. However, there have been several reports stating that eSata was faster than USB3 on other systems too.

Conclusion

Yes, USB3 provides fast data transfer speeds. But, there are no disks on the market right now that can exploit that capability. Rotating disks are probably maxed out with the 10.000RPM Raptors and SSDs are still too expensive for large amounts of data storage – and even the SSDs of today would not use the full USB3 capability.

I suppose we have to wait for the future developments in the disk technology to make full use of USB3. But then there is already Thunderbolt offered by Intel and Apple which provides PCI-E type performance for an external attachment. There is always the next step.



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My System SpecsSystem Spec
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24 Apr 2011   #2

Windows 7 ultimate X64
 
 

Very informative article Wolfgang. I am just now playing with my first SSD and I must say performance isnt what I expected, although MUCH better that rotating drives.
My System SpecsSystem Spec
24 Apr 2011   #3

 
 

Excellent artical, Wolfgang.
Great for us novices to get a better handle on things.
My System SpecsSystem Spec
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24 Apr 2011   #4

Windows 7 Ultimate x64
 
 

Of course, given the exact same hard drive...which provides a certain amount of speed given the physical drive itself.....in almost every situation I have read about, the performance is faster with eSATA than it is with USB 3.0....even though from a theortetical perspective, USB3.0 provides room for 2x the performance. I think THAT is the part that really confuses people. I believe it has to do with USB3.0 overhead, and driver support for the USB 3.0 chipsets at the present time.
My System SpecsSystem Spec
24 Apr 2011   #5
whs
Microsoft MVP

Vista, Windows7, Mint Mate, Zorin, Windows 8
 
 

Yes right. On one of my systems I have both USB3 and eSata, but I always use eSata for imaging. It is indeed faster. If only the eSata cable would not be so stiff.
My System SpecsSystem Spec
24 Apr 2011   #6

Windows 7 Ultimate x64
 
 

I don't even give USB3.0 a thought these days. I just make sure what I want to use has eSATA since that gives me best performance.
My System SpecsSystem Spec
25 Apr 2011   #7

Several, including Windows 7 x64 Ultimate
 
 

Quote   Quote: Originally Posted by whs View Post
Yes right. On one of my systems I have both USB3 and eSata, but I always use eSata for imaging. It is indeed faster. If only the eSata cable would not be so stiff.
Same here.

Have you tried running a USB 2.0 drive on a USB 3.0 port? You might be surprised!

Regards....Mike Connor
My System SpecsSystem Spec
25 Apr 2011   #8

Microsoft Community Contributor Award Recipient

Windows 7 Ult x64 - SP1/ Windows 8 Pro x64
 
 

Nice post Wolfgang.

I use eSATA also, hopefully USB3 will evolve.
My System SpecsSystem Spec
25 Apr 2011   #9
whs
Microsoft MVP

Vista, Windows7, Mint Mate, Zorin, Windows 8
 
 

Quote   Quote: Originally Posted by Mike Connor View Post
Quote   Quote: Originally Posted by whs View Post
Yes right. On one of my systems I have both USB3 and eSata, but I always use eSata for imaging. It is indeed faster. If only the eSata cable would not be so stiff.
Same here.

Have you tried running a USB 2.0 drive on a USB 3.0 port? You might be surprised!

Regards....Mike Connor
Hi Mike, I am afraid you lost me a bit. The first to measurements above were with the same drive on USB2 and USB3. Is there something else I should expect and I have missed?
My System SpecsSystem Spec
25 Apr 2011   #10

Several, including Windows 7 x64 Ultimate
 
 

Quote   Quote: Originally Posted by whs View Post
Quote   Quote: Originally Posted by Mike Connor View Post
Quote   Quote: Originally Posted by whs View Post
Yes right. On one of my systems I have both USB3 and eSata, but I always use eSata for imaging. It is indeed faster. If only the eSata cable would not be so stiff.
Same here.

Have you tried running a USB 2.0 drive on a USB 3.0 port? You might be surprised!

Regards....Mike Connor
Hi Mike, I am afraid you lost me a bit. The first to measurements above were with the same drive on USB2 and USB3. Is there something else I should expect and I have missed?
Running a USB 2.0 drive on a USB 3.0 port produces some odd results on various systems. But it is usually a lot faster than running a USB 2.0 drive on a USB 2.0 port.

I have tested a few and was rather surprised at the results, because although USB 3.0 is legacy capable ( backward compatible) to USB 2.0. It should not be faster than 2.0 if the drive is only 2.0 capable, but they almost always are, and by an appreciable amount.

If I get time tomorrow I will hook a few up and run a few tests.

On my personal machines I now only use eSATA.

Regards....Mike Connor
My System SpecsSystem Spec
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