But you don't see too many relatively simple devices like
that suffer two completely different very serious faults.
Not so unusual when you run the device for 24/7 for months on end. When
it was being run as a PVR drive, it was never shut-off, even if the PVR
itself was off. The drive had to always be ready to record something, as
soon as the PVR woke up, so the drive itself could never sleep.
You can get delayed results like that, particularly when the power
supply seriously over voltages the system for a short time.
I don't disagree that both types of damage might have been done during
the time it was in that enclosure, but I don't agree that there was ever
any single event that was responsible for both failures. The damage to
the internal drive was likely caused by the excessive load/unload cycles
over time while it was inside the enclosure, which is basically a
mechanical failure. What caused the enclosure's interface electronics to
die was something else entirely, details not fully determined yet, but
this one could only be electronic/electrical in nature.
Harder to explain the weird symptom that the write speed
obviously varys with where the head is on the platter that
way tho and that only affecting writes, not reads.
If we ever do work out what the fault is due to, bet we
will kick ourselves for not thinking of that earlier tho.
I don't think so. I don't think a common explanation is needed for both
failures, necessarily. I'll explain why below.
BTW, I had written about this drive's history before on this newsgroup
(Google Groups):
http://is.gd/tkqeKJ
Back then, the drive was still inside its My Book enclosure, and I was
having some kind of problem with reading SMART data out of it through
its eSATA interface. It was during this thread that I was first
introduced to HD Sentinel.
The My Book contained a bridging chipset that acted as the interface
from the hard disk to the computer, offering USB, Firewire, and eSATA.
What we didn't know back then was that the chipset was manufactured by a
company called Oxford Semiconductor. This chipset contained its own ARM
processor. So it was an intelligent interface controller. If the ARM
chip failed somehow, then it would mean the interface is dead, but not
necessarily the disk inside.
http://en.wikipedia.org/wiki/Western_Digital_My_Book#Internals
Cant see how that would produce that very unusual symptom
of the write speed so dramatically affected by the location of
the head on the platter, and not the read speed.
The HD Sentinel tech believes that the excessive load/unload cycles
might have damaged the head parking area of that drive. This might have
resulted in microscopic dust particles covering the platter which made
it harder to re-magnetize the platter near the parking area. Since the
parking area is near the front of the platters, this is the area that
was first affected. He suggested that this dust is just going to keep
creeping towards the back of the drive, until the entire surface is
unusable. The fact that there are some areas which are alternately fast
and slow (i.e. the "Slow", "Medium" and "Fast" sections of the drive) is
an indication that this backward creep is already happening.
It's a theory, don't know if it's the only possible theory.
They certainly are notorious for unloading much too frequently.
Havent see anyone report that weird write speed result with them tho.
Now that I know that this Western Digital load/unload issue has come up
before on this newsgroup, I would like to know how other people
determined that this was a problem? I think Arno was one of the first to
express concern over this load/unload issue, but I don't quite know what
led him to believe that it was a problem? I realize we're getting into
historical issues here.
Yousuf Khan
