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Re: External hdd changing device node mid-use

On Tue, 21 Dec 2010 06:58:55 +0200, Panayiotis Karabassis wrote:

> Thanks all. I tried toying with udev to create a persistent node name,
> but to no avail. The problem seem to be that the hdd is periodically
> disconnecting. By the time it has disconnected, it is too late. Md has
> already faulted the device. If anyone has any ideas about preventing the
> drive from disconnecting... I tried running sdparm in a cron job, as I
> read somewhere, but it didn't work. I suspect it is disconnecting by
> design, as this as an external usb-powered disk. It's model is LG HXD5
> 320GB if it helps.

I see here two possible causes for the random disconnects:

1/ USB hard disk has embedded in firmware a power management routine that 
puts the drive into sleeping state if no actitivy is detected in a given 
interval of time. But if the drive is inside an array, this shoud not 
happen. Also, you are running a cron task with a job that should prevent 
the device from going down :-?

2/ USB hard disk is not getting enough power. If it is being powered by 
the USB port maybe this is not providing the required voltaje to the 

Another possibility is the USB cable, as Johann pointed out.



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