What does G mean?

[mm]

From the specs of a hard drive:

# Shock (1/2 sine pulse):

* Operating: 70 G
* Non-operating: 300 G

What does G stand for? Surely not "the force of gravity", as in,
During laundh astronauts are subjected to 10 G" or some number of
them.

 

[Bob Willard]

From the specs of a hard drive:

# Shock (1/2 sine pulse):

* Operating: 70 G
* Non-operating: 300 G

What does G stand for? Surely not "the force of gravity", as in,
During laundh astronauts are subjected to 10 G" or some number of
them.

Yes indeed, G means the force of Gravity in specs for shock and
vibration.

 

[Arno]

From the specs of a hard drive:

# Shock (1/2 sine pulse):

* Operating: 70 G
* Non-operating: 300 G

What does G stand for? Surely not "the force of gravity", as in,
During laundh astronauts are subjected to 10 G" or some number of
them.

Gravity as acceleration (the two are equivalent with the
right frame-transformation). 1G = 9.81m/s^2

Arno

 

[Man-wai Chang]

# Shock (1/2 sine pulse):

* Operating: 70 G
* Non-operating: 300 G

Physics.

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[Rod Speed]

mm wrote

From the specs of a hard drive:

# Shock (1/2 sine pulse):

* Operating: 70 G
* Non-operating: 300 G

What does G stand for? Surely not "the force of gravity", as in,
During laundh astronauts are subjected to 10 G" or some number of
them.

Yes, that is what it means.

 

[mm]

"mm" inquired:

This means that in operation (i.e. with the R/W head over the
platter), the unit can withstand an acceleration peaking at 70g,
where "g" is the acceleration of a mass at the earth's surface due to
gravity, i.e. 32 ft/sec/sec. The graph of the acceleration vs. time
would be that of 1/2 of a sine wave. In structural mechanics, though,
the length of time taken for that acceleration to peak (a measure of
"jerk") would also be significant, and it's not in those specs.

*TimDaniels*

Thanks all.

So they're claiming that the harddrive can withstand a shock of 70
times the acceleration of gravity while the drive is operating without
crashing? Or without failing entirely? Or what?

How would this compare with the shock resistance of a *laptop*
harddrive made in 2000, for example?

 

[Yousuf Khan]

Thanks all.

So they're claiming that the harddrive can withstand a shock of 70
times the acceleration of gravity while the drive is operating without
crashing? Or without failing entirely? Or what?

How would this compare with the shock resistance of a *laptop*
harddrive made in 2000, for example?

Don't know how it compares to hard drives from ten years ago, but I
think hard drives have been built to similar specs for quite some time
now. They've only been getting bigger and faster, but their physical
dimensions have stayed constant.

The 70 G or 300 G figures would probably correspond to somebody dropping
a running or stopped server from a height of a few feet respectively,
and it coming to a sudden stop on the floor.

Yousuf Khan

 

[Rod Speed]

mm wrote
Yes, but you get much bigger shocks when you drop something onto a hard surface etc.

Thanks all.

So they're claiming that the harddrive can withstand a shock of 70 times
the acceleration of gravity while the drive is operating without crashing?
Yes.

Or without failing entirely?

Without failing at all.

Or what?
Nope.

How would this compare with the shock resistance
of a *laptop* harddrive made in 2000, for example?

It hasnt changed significantly.

Laptop drives have always had significant shock ratings,
because they can see that when put down on tables hard etc.

 

[Rod Speed]

Mark F wrote

Yes it has.

No it hasnt.

See, for example:

http://www.seagate.com/www/en-us/products/laptops/laptop-hard-drives/#tTabContentSpecifications
Momentus Laptop Hard Drives with G-Force
350G operating, 1000Gs non-operating

It clearly hasnt changed significantly with the drive he quoted the spec of.

NOTES:
I think that the ratings on all rotating drives usually means "one time".

You're wrong.

In other words, the ratings are not "operating" ratings.

How odd that the word operating is used in the specs.

You'd have to look further into the ratings to see
what would the rating for an operating environment,
such as use in a GPS system in a car

That was true of laptops in 2000.

(although nowadays you'd be using solid memory in a GPS.)

Only a tiny subset ever had rotating hard drives.

 

[Rod Speed]

"operating" means "spinning" in the specs.

Thats the same thing, different words.

As to how often the shock can be repeated, I rechecked the Seagate
Barracuda 7200.11 Serial AT Product Manual, publication number
100507013, Rev. E (as an example). It seems like the "2.8.5.1
Operating shock" says no more than 2 times per second and
"Nonoperating shock" says "nonrepetitive", so I guess I was
wrong: the operating shock seems to be repeatable many times,
and just the non-operating shock has a low repeat count (1 total).

Nope, that last just means that it isnt a repetitive shock, not that it can only be done once