Determining hard drive state

[Matt Graham]

After a long battle with technology, Alan Dayley wrote:
> On Sat, Nov 14, 2009 at 11:32 AM, Kirk Bauer <kirk at kaybee.org> wrote:
>> I have a laptop with two hard drives: an SSD running Ubuntu 9.10 and a
>> regular hard drive with Windows 7.  My hope is that the spinning drive
>> is normally not spinning, but I can't hear it, and I can't figure out
>> how to tell (from Linux) if it is powered on or not.

"hdparm -C /dev/whatever" should tell you.  Disks that are spinning show up as 
active/idle, disks that are not should be standby or sleeping.  Disks that 
are USB give me a set of weird SCSI errors and "unknown", though, so YMMV on 
this.

> By default, if the hard drive has power, it is spinning.  Unless the
> host computer commands it to spin down, it is spinning. Oh, and most any
> command sent to the drive by the host will cause it to spin back up.  Linux
> usually does not do this but configurations vary.

In general, you won't be able to spin down any disk that 
contains / , /var , /usr , or /home unless nobody's logged in.  

-- 
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Matt G|There is no Darkness in Eternity/But only Light too dim for us to see