Problem Mounting WD Passport External HD


7 posts
by qkzoo » Sun Mar 10, 2013 2:00 pm
I just bought an external WD My Passport 1.5gb drive. I loaded it on a linux machine and left it as a single partition, formatting it as ext4. I connected it to the Pi, and it sees it as sda, but it won't mount it. When I try, using:
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sudo mount -t ext4 -o uid=pi,gid=pi /dev/sda /media/USBDRIVE/

I get "/dev/sda" is not a valid block device.

If I use:
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sudo mount -t ext4 -o uid=pi,gid=pi /dev/sda1 /media/USBDRIVE/

I get:
mount: special device /dev/sda1 does not exist

However, when I do a:
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tail -f /var/log/messages


I see the device listed as sda, but it does say "Spinning up..." for a long time, and then "......................................not responding".

I have the drive plugged into a powered USB hub attached to the pi. Could this be an under-powered hub? It's the only thing I can think of at this point. I could use an experts opinion, though, as I'm most definitely not!

Q
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by joan » Sun Mar 10, 2013 3:01 pm
You need to use /dev/sda1 when mounting.

If it's a 5" disk it's probably a power problem. I seem to remember you could get Y cables so that two usb ports could power a single drive.
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by qkzoo » Sun Mar 10, 2013 3:21 pm
Thank you, I will look for one and try it out.
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by qkzoo » Fri Mar 15, 2013 9:25 pm
...so I got a dual usb cord, and I'm still having the same problem. When I try to mount it as before (using sda1) I get a message:

mount: special device /dev/sda1 does not exist


I did notice this time, when I ran the tail -f /var/log/messages :

raspberrypi kernel: [..........not responding...
[sda] READ CAPACITY failed
[sda]


...and then a few other items were on there, recognizing it as a scsi disk, etc. Any ideas, I'm really stumped!
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by FTrevorGowen » Fri Mar 15, 2013 9:51 pm
The dual usb (Y) cord may have helped a little but, in my experience, and based upon measurements of the loading performance and inter-connectivity of the ports of a number of "powered hubs" (albeit "low-cost" ones) it's the hub's PSU that's the "critical" component. Many external disk drives need at least 1 amp on "spin-up" and the PSU/hub combination has to be able to provide this. The USB specs. "state" that each port can supply up to 500mA (hence the Y cable to connect to two ports). However, virtually all of the hubs measured had the "power connections" of their ports connected in parallel - hence all the Y cable does is give you a little reduction in the combined connector/cable resistance. (More detail can be found in my webpages - see link on the right). I have a DVD drive which uses a Y lead and works fine if plugged into two ports of my netbook (it was originally supplied with a Medion laptop some years ago). However, in order to get it to work (ie. mount) via a powered hub I had to power the hub with an "ILuv" 5V 2A PSU.
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Mainly running "Wheezy Raspbian" on four Pi's (an A, B1 & 2xB2). Notes about them begin at http://www.cpmspectrepi.webspace.virginmedia.com/raspberry_pi/raspiidx.htm
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by qkzoo » Fri Mar 15, 2013 10:05 pm
I think that you're probably right. Can you, or anybody else recommend a powered USB hub for this task?
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by FTrevorGowen » Fri Mar 15, 2013 10:25 pm
See http://elinux.org/RPi_VerifiedPeripherals for a few . Personally I suggest the Hama "Kidney" shaped hub I've investigated. The Targus hub and the Gemini switching hub should be OK too - the latter enables you to switch between two computers - I use it to share an external mouse and keyboard between my netbook and a Pi (sharing of the monitor is done by the netbook being VGA and a Pi being HDMI). However you will need a good PSU too - again see the first link, and also my webpages. NB: the hubs mentioned should not "back-power" the Pi.
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