hi !

> Emulex uses Seagate ST-82272J drives in the SD893 unit.  Seagate's spec
> sheet lists
> the interface as SMD E.  However, here's what Emulex wrote in their User'=
s
> Guide:

[...]

> spin error) on the front panel.  Is the servo information something that
> can only be
> restored by the manufacturer?  If the servo info can be restored, would t=
he
> drive then
> require standard reformatting?

To explain this problem, i=B4ll explain how the servo tracks work and why t=
hey
are needed. Modern hard disk (and your big SDI disks) don=B4t use a stepper=
 motor
to control the head position and to seek a special track, they use a simple=
=20
voice coil, which pulls the heads outwards. The rotation of the disk media
is the other force and pulls the heads inside. This means, if power is turn=
ed
off, the heads mode inside, towards the spindle. Positive side-effect: this
is called "autopark" :-) Ok, so you see: you need a specific voltage to for=
ce
the heads to the outer tracks of the media. This voltage is analog, and may
vary with the temperature of the drive. So you need something very digital =
to
get the D/A-converter to control the voice coil giving the correct voltage =
to
seek to a specific track. This is done by this servo information. I know fr=
om
an RA81, the servo information is separated on one surface, which is dedica=
ted
for these servo informations. Other drives (newer PC drives) can also use
embedded servo, there the information is embedded into the data tracks on t=
he
media.

To avoid lots of seeking, the drive does a "first-seek" after spinning up, =
it
just outputs some voltages and looks for the tracks. Some values are stored=
 in
RAM, maybe highes, middle and lowest track or so. So the drive calculates t=
he
relative voltage value per track and can "jump" to the right area and do th=
e
fine positioning very quick. During runtime, these data will be re-measured
every some minutes, this is why the drives sometimes move, even if there is
absolutely no access. (thermal recalibration...)

To get the anser to your question in simple words: Servo tracks can=B4t be
written by the drive, if there is absolutely no information, where the trac=
ks
are. The servo media can only be written with a special writer, which contr=
ols
the head by a stepper motor or so. If the servos are damaged, the drive is
trash. Sounds hard, but they can only be restored by the manufacturer. The =
rest
of the drive would only need a low-level format. But not knowing, where the
tracks have been, this won=B4t work. So i think, error 4D might mean someth=
ing
like: unable to get servo information.

so long... Michael