Re: Interesting speed benchmarks

On 01/26/07 12:49, Warner Losh wrote:
From: Stefan Ehmann <shoesoft@xxxxxxx>
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




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