[ltp] External USB drive

[Eben King]

On Thu, 19 Aug 2004, Hector Socas Navarro wrote:

> 	I recently purchased a 200Gb extrenal hard drive (USB 2). When I 
> started using it I found it painfully slow so I used hdparm to test its 
> speed:
> 
> [root@sauron root]# hdparm -Tt /dev/sda
> 
> /dev/sda:
>   Timing buffer-cache reads:   128 MB in  0.38 seconds =336.84 MB/sec
>   Timing buffered disk reads:  64 MB in 93.69 seconds =699.50 kB/sec

Make sure you have a USB 2.0 driver loaded for the port, not USB 1.1 .  
That got me on my desktop.  USB 1.1 is usb-uhci or usb-ohci (there are a 
few others but those are the biggies); USB 2.0 is ehci-hcd.

> Something's very wrong here. I should be getting ~40 MB/sec, right?

Somewhere around there.  From /usr/src/linux/Documentation/usb/ehci.txt:

.--
| The EHCI driver is used to talk to high speed USB 2.0 devices using
| USB 2.0-capable host controller hardware.  The USB 2.0 standard is
| compatible with the USB 1.1 standard. It defines three transfer speeds:
|
|     - "High Speed" 480 Mbit/sec (60 MByte/sec)
|     - "Full Speed" 12 Mbit/sec (1.5 MByte/sec)
|     - "Low Speed" 1.5 Mbit/sec
'--

> I'm running RedHat 7.3 with some updates and kernel 2.4.22 on a T30

You may need to upgrade your kernel if you don't see "EHCI HCD (USB 2.0) 
support (EXPERIMENTAL)" in your kernel config options.  I'm using 2.4.26 
here.

-- 
-eben    ebQenW1@EtaRmpTabYayU.rIr.OcoPm    home.tampabay.rr.com/hactar

A: Because it looks dumb and is hard to read.
Q: Why is top-posting wrong?  -- from lots42@xxx.com