Access openings in HDDs

[Rod Speed]

Is the formatting on one side only, with alternating data and formatting
tracks?

There are no alternating data and servo tracks anymore,
they are long gone now like dedicated servo surfaces too.

Why don't they do it before the cover is on, instead of having a
vulnerable spot that could be accidentally punctured?

Some have the heads screwed onto the cover.

I suppose many drives are done that way because they have no holes.

Yep.

 

[Arno]

Is the formatting on one side only, with alternating data and formatting
tracks?

I think modern disks have servo tracks on every surface, because the
surfaces are not aligned well enough for just on surface to serve
them all.

Why don't they do it before the cover is on, instead of having a vulnerable
spot that could be accidentally punctured? I suppose many drives are done
that way because they have no holes.

Because of the precision involved, it is done as late in the assembly
process as possible. And to be fair, puncturing these is failry
unlikely.

Arno

 

[Rod Speed]

I think modern disks have servo tracks on every surface,

They actually have servos embedded in every track on every surface.

because the surfaces are not aligned well
enough for just on surface to serve them all.

That can't be true of single platter drives.

Because of the precision involved, it is done as late in the assembly
process as possible. And to be fair, puncturing these is failry unlikely.

Doesn’t explain why so many drives don’t have them.

Or why they arent plugged with something a lot
more substantial than just flexible foil and plastic.

 

[larrymoencurly]

Modern HDDs cannot low-level format themselves with regard
to the servo tracks. These openings serve to insert the
formatting heads. And yes, they go straight inside. Arno

About a dozen years ago, IBM ammounc that their UltraStar
drives could write their own servo tracks, without external
equipment? Is that still used, or are today's tracks too narrow?

 

[larrymoencurly]

Some HDDs have rather large (1cm) holes covered by plastic and foil stickers. They seem to be positioned for easy access to destroying the platters with a screwdriver or something. Is that what it's for? -- Reply in group, but if emailing add one more zero, and remove the last word.

 

[Rod Speed]

Arno wrote

About a dozen years ago, IBM ammounc that their UltraStar
drives could write their own servo tracks, without external equipment?

Cant see how that is possible when the servo
tracks are needed to position the heads. How do
you position the heads without any servo tracks ?

Is that still used,

I'm not convinced that it ever was with voice coil drives.

or are today's tracks too narrow?

Without it being clear what they were actually
claiming to be able to do, its hard to say.

And the other obvious question is that even
if it is possible, why is that better than using
external equipment when you have to have
that to assemble and test the drive anyway ?

 

[larrymoencurly]

Can't see how that is possible when the servo tracks are needed
to position the heads. How do you position the heads without
any servo tracks ?


I'm not convinced that it ever was with voice coil drives.

Wouldn't they need only

Here's something by IBM about this:

https://www1.hgst.com/hdd/research/images/as images/servowrite.pdf

And here's somebody else's technical paper:

http://www.me.berkeley.edu/~horowit...rs_numbered/186c_Nie_ACC10_TutorialonSSTW.pdf

 

[Rod Speed]

Wouldn't they need only

Here's something by IBM about this:

https://www1.hgst.com/hdd/research/images/as images/servowrite.pdf

Doesn't say anything about how you position the heads when
there are no servo tracks for the head positioning system to use.

And here's somebody else's technical paper:

http://www.me.berkeley.edu/~horowit...rs_numbered/186c_Nie_ACC10_TutorialonSSTW.pdf

And neither does that.

 

[Tom Del Rosso]

Doesn't say anything about how you position the heads when
there are no servo tracks for the head positioning system to use.


And neither does that.

They must write one side before assembly.

Then it has to be mounted exactly on center though.