SATA disks suddenly stop working

Gary Jennejohn gary.jennejohn at
Fri Mar 6 10:55:04 PST 2009

Back to the saga of problems with AHCI.

Yesterday I had one of my problem disks in a dockingstation, which was
attached per USB2 with the disk mounted.

When I shut down the machine I noticed that the disk suddenly spun up.
Evidently it spun itself down (I didn't know it would do that) and
the USB stack (or something) noticed it and forced it to spin back up.

This gave me a clue as to what might have been causing my problems with
this disk.

So today I attached it per eSATA and mounted it.  I started a small shell
function which touches a file on the mounted file system every 60 seconds.
I figured that would force the disk to stay spun up.

The disk has been running all day without any problems.  Normally, after
an hour or so of inactivity any access to the drive would produce lots
of errors and require a POR to recover.

This leads me to conclude that nost of the problems which I've seen had
nothing to do with the driver, but were caused by the disk itself.

Perhaps the driver could try to spin up a disk if a command fails,
although I'm not certain how the driver could determine that, ie. spun
down, as the cause of any errors.  But as I wrote above, _something_ spun
the disk back up when it was attached per USB.

Gary Jennejohn

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