[dm-devel] Hard drives shutting themselves off in RAID mode

Arno Wagner wagner at tik.ee.ethz.ch
Sun Jun 18 18:50:21 UTC 2006


On Sun, Jun 18, 2006 at 03:45:36PM +0200, Rune Saetre wrote:
> Hi
> 
> >Arno Wagner:
> >>If you can test it with reasonable effort and cost (e.g. put some of
> >>them on another PSU), you might want to do that.
> >
> >Is that safe?
> 
> Don't know how safe it is to use different PSU's, but I have done it with 
> success several times on old hardware used for testing. I can't think of 
> any reason you should run into trouble if ground is common, and the disks 
> are powered up first.

It is pretty safe, as long as you plug both PSUs into the same
outlet and the outlet its grounded. Also powering up may be a bit
difficult, since the power-up signal comes from the mainboard today.

Better solution: Get a PSU with more power reserves and try with that.
>From the time you have alreasy sunk into this problem, I gather 
paying for a, say, 500W PSU would not be too bad.
 
> >Another way could be to use a meter to gauge how much power it drains.
> 
> You better use an oscilloscope if anything, as you are looking for very 
> short transients. I have heard (but never tested) that the disks pull 
> large currents when moving the heads, but with seek times of some 
> milliseconds you wouldn't even see it on a regular amperemeter.

Nor a regular oscilloscope. Would need to be the storage kind.
Expensive, unless you can borrow it.

Arno

-- 
Arno Wagner, Dipl. Inform., CISSP --- CSG, ETH Zurich, wagner at tik.ee.ethz.ch 
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