[ltp] Re: Making hard drive stop when not in use

[morpheus]

I agree...my motto is:
EXPECT yuor hard drive to fail. It's not a matter of "if" but "when"...
ALWAYS back up...today could be your unlucky day!

On Sat, 2004-10-02 at 23:31, Theodore Ts'o wrote:
> On Fri, Oct 01, 2004 at 05:48:32PM -0500, Rob Browning wrote:
> > Juergen Stuber <juergen@jstuber.net> writes:
> > 
> > > it is very easy to configure so that it also spins down the harddisk
> > > when on AC, I also do it to prevent the drives from wearing out.
> > 
> > Hmm.  I'd gotten the impression that it was starts/stops (and head
> > parks/unparks) that were the primary wear on the drive, not continuous
> > spin.
> 
> It's both, actually.  There are a couple of things that can cause wear
> on a drive, thus shortening its life:
> 
> 1.  Landing/takeoff cycles on the drive (which happen every time the
> drive is spun up or down).  The disk drive heads are pushed down
> towards the patters by springs, and when the disk starts spinning, the
> head drags along the platter until the disk is going fast enough that
> an air cushion is established that aerodynamically pushes the hard
> drive heads away from the platter.  When the drive stops spinning, the
> air cushion disappears and the springs push the head towards the
> platter.  The probability of failure caused by wear and tear on the
> hard drive dragging across the surface of the drive increases
> geometrically with each landing/takeoff.  Modern drives are generally
> engineered such that P_failure reaches 50% after 50,000
> landing/takeoff cycles.
> 
> 2.  The life of the motor.  The motor/ball bearings on some hard
> drives may not be engineered for continuous operation.  So if the disk
> is spinning continuously, this may also shorten the life of the drive.
> In particular, some desktop drives and most laptop drives are *not*
> engineered for continuous operation.  Desktop drives because the hard
> drive manufacturers are trying to save pennies on each drive so they
> can make a profit even when Wal-Mart and Dell are forcing them to
> lower prices every other day.  Laptop drives because they are
> constrained by power and space limitations.
> 
> 3.  Thermal issues.  Some hard drives are installed without sufficient
> heat sinking so they can withstand being operated continuously.  A
> good example of this is the hard drive in the iPod.
> 
> 
> The bottom line is that any time you use the hard drive, you will be
> causing wear and tear, whether it is by spinning the hard drive or by
> causing the heads to take off and land repeatedly.  Different hard
> drives are engineered with different lifetimes in mind, but
> ultimately, hard drives do not last forever.  2-3 years if you're
> lucky, and if you're truly paranoid, and given how cheap hard drives
> are, upgrading them with a newer, bigger model every 18-24 months is
> not a bad idea.
> 
> 						- Ted