Re: Interesting speed benchmarks

On 01/26/07 12:49, Warner Losh wrote:
> From: Stefan Ehmann <shoesoft_at_gmx.net>
> Subject: Re: Interesting speed benchmarks
> Date: Fri, 26 Jan 2007 10:52:11 +0100
> 
>> On Friday 26 January 2007 03:24, M. Warner Losh wrote:
>>> On a lark, I just got a combo USB/Firewire external disk drive.  I ran
>>> some crude benchmarks, and I was surprised by what I found.  This is
>>> on a fairly stock -current kernel.
>>>
>>> Firewire does around 40MB/s, while USB 2.0 maxes out at about 12MB/s.
>>> This is with a simple dd command:
>> On my i386 notebook with USB 2.0 enclosure.
>> Linux: 31.5MB/s
>> FreeBSD: 27.5MB/s
>>
>> There's still room for improvement but numbers don't seem that bad.
>>
>> Maybe you should try knoppix or so to verify it's not the drive's fault. Other 
>> than that I'd also guess it's an amd64 problem.
> 
> It is not an AMD64 problem.  I get the same numbers on my i386 latpop
> as I get on my amd64 laptop.  Actually, I get WORSE numbers on the
> i386 laptop by about 20%.
> 
> It isn't the drive's fault.  Otherwise, firewire wouldn't get 40MB/s.
> The same drive, the same enclusure are used for both the USB and
> firewire tests.  It is about as apples to apples as you can get.
> 
> There's some serious performance issues in the usb stack.
> 
> Warner


A few tidbits of information (may be useful, maybe not):

- I've seen the firewire part of the enclosure be faster than the USB 
part.  The chips that run it are possibly different, so that shouldn't 
be forgotten.  I've had a few USB->flash adapters that got lousy 
performance, but when I switched to a USB->SATA flash card reader, the 
performance doubled.

- For those testing using a file system - STOP! It's not a good test of 
the throughput of the device, and depends on a lot of variables.  dd or 
diskinfo are decent generic tools, but in Windows you just can't use a 
file system benchmark to compare.

- If you read/write less than the drive cache, it should remove the 
latency of the drive from the equation, right?

Eric