[mythtv-users] External storage spin up time - mythfrontend sometimes times out

[Simon Hobson]

Saul <jaglover at gmail.com> wrote:

> Actually if I think of it ... it was the load cycle count that went up.
> And the RAID was lazy to react after long time no access. After running
> idle3ctl on them the load cycle count stopped and laziness is gone. So
> does a load cycle involve spindown?

Ah, that's another setting.
WD drives will retract the heads from the disk* and park them when idle - putting them back over the disk when access is required - this is a load cycle. Doing so reduces aerodynamic drag and hence power needed to keep the disks spinning, and is a pre-requisite to letting the disks spin down.

I believe some drives will slow (but not stop) the disks once the heads are parked - no idea if WD do this - which also reduces power but leaves the disks "almost ready" for use.

On WD Green drives, the head retraction is done very aggressively after only a few seconds IIRC - which in normal use on a multi-tasking OS results in a rapidly increasing load cycle count. I think people here have suggested the drives have a maximum for this and WD will consider the drive "worn out by use" rather than faulty if it's very high - at a value reachable by only a few months of "normal" use. Hence advice to increase the time before it's done.

All very high tech for those of us who remember when you had to run a utility to park the heads before switching off, and in some cases even re-inserting a locking screw before moving the PC !


* I think the heads are either lifted, or more likely, moved to where a "ramp" will physically hold them off the disk. Early drives just let the heads land on the disk surface when spinning down, and kept a dedicated area (no data stored) for landing. This doesn't work if the drive is allowed to spin down when idle due to the wear during takeoff and landing when the heads are sliding on the disk surface.