Hard drive free fall sensor?

[larry moe 'n curly]

How much does a free fall sensor help protect a hard drive?

Why are some drives designed to handle 2 free fall sensors? Samsungs
since at least the F1 Spinpoints are like this, and their 2TB HD204UI
seems to usually include just one such sensor.

 

[Rod Speed]

How much does a free fall sensor help protect a hard drive?

Nada, zero, zip.

Why are some drives designed to handle 2 free fall sensors?

Because that allows the manufacturers to deny a warranty claim.

Samsungs since at least the F1 Spinpoints are like this, and their
2TB HD204UI seems to usually include just one such sensor.

Because with the better sensors, thats enough.

 

[Arno]

How much does a free fall sensor help protect a hard drive?

Why are some drives designed to handle 2 free fall sensors? Samsungs
since at least the F1 Spinpoints are like this, and their 2TB HD204UI
seems to usually include just one such sensor.

These are acceleration sensors and have axes. If you only
use a 1-axis acceleration sensor, you can only detect a fall
in one direction. I would expect that is along the spin-axis
of the disk, that being the most sensitive and the way the
computer is typically oriended with regard to gravity.

Now, the thing these acceleration sensors detect duting
a fall, is the absence of gravity. If you orient the disk
vertically, a sensor designed to detect a fall when oriented
horizontally will not detect gravity and will not detect
a fall.

Anyways, these devices can detect a clean fall and
retract the heads. Thay are more limited on short falls
(e.g. 5cm onto hard desktop) and additional mechanical
buffering is needed in any case. I have no numbers, but
my WAG is that you get a surviving harddrive in 50%-80% of
the cases were a fall killed it earlier.

Now, there are 3-axis sensors on the market, that do not
suffer this limitation. I have no idea what using 2 sensors
accomplishes and suspect using one 3-axix sensor is cheaper
than using 2 1-axis sensors. Also I found a 3-axis sensor
at a 1-pice end-user price of about 4EUR, which indicates
these are not expensive in the first place. The 2 sensors
may just be a marketing stunt. Or maybe you can get 1-axis
sensors extremely cheap.

Arno

 

[Franc Zabkar]

How much does a free fall sensor help protect a hard drive?

Why are some drives designed to handle 2 free fall sensors? Samsungs
since at least the F1 Spinpoints are like this, and their 2TB HD204UI
seems to usually include just one such sensor.

Are you referring to standard shock sensors, or tri-axis
accelerometers?

Typical shock sensors are mounted at a 45 degree angle in order to
detect vibration in both horizontal axes. The outputs from these
sensors are used to provide a compensation signal which is injected
into the voice coil servo control loop. Often there will be an
associated dual op-amp to buffer and amplify the signal. Otherwise
this circuitry is internal to the motor controller.

The tri-axis accelerometer detects movement in three axes. It is this
component that provides the free-fall detection capability. AIUI, it
is usually implemented as an all-in-one IC, rather than as a discrete
sensor with external signal conditioning circuitry.

Here is a review of Samsung's Spinpoint F4EG (HD204UI):
http://www.storagereview.com/samsung_spinpoint_f4eg_review_hd204ui

I can see three shock sensors in this photo:
http://www.storagereview.com/images/samsung-f4eg-pcb-top.jpg

There is one white device to the right of the Samsung SDRAM, a second
similar device at about 11 o'clock to the SH6125B motor controller IC,
and a third, smaller device above that same IC.

I can't see any accelerometer.

Here are some datasheets:

Murata ceramic shock sensors:
http://www.farnell.com/datasheets/58860.pdf
http://www1.futureelectronics.com/doc/MURATA/PKGS-00LD-R.pdf

KXPB5, Kionix, Tri-axis Accelerometer:
http://www.kionix.com/Product Sheets/KXPB5 Product Brief.pdf
http://www.kionix.com/Product-Specs/KXPB5-2050 Specifications Rev 3.pdf
http://www.kionix.com/Product-Specs/KXPB5-2353 Specifications Rev 3.pdf
http://www.kionix.com/accelerometers/accelerometer-KXPB5.html

- Franc Zabkar

 

[Arno]

Are you referring to standard shock sensors, or tri-axis
accelerometers?

Typical shock sensors are mounted at a 45 degree angle in order to
detect vibration in both horizontal axes. The outputs from these
sensors are used to provide a compensation signal which is injected
into the voice coil servo control loop. Often there will be an
associated dual op-amp to buffer and amplify the signal. Otherwise
this circuitry is internal to the motor controller.

That would make sense and explain the two sensors. As the
platter spin in one plane, two sensors would cover platter
vibrations.

Arno

The tri-axis accelerometer detects movement in three axes. It is this
component that provides the free-fall detection capability. AIUI, it
is usually implemented as an all-in-one IC, rather than as a discrete
sensor with external signal conditioning circuitry.

Here is a review of Samsung's Spinpoint F4EG (HD204UI):
http://www.storagereview.com/samsung_spinpoint_f4eg_review_hd204ui

I can see three shock sensors in this photo:
http://www.storagereview.com/images/samsung-f4eg-pcb-top.jpg

There is one white device to the right of the Samsung SDRAM, a second
similar device at about 11 o'clock to the SH6125B motor controller IC,
and a third, smaller device above that same IC.

I can't see any accelerometer.

Here are some datasheets:

Murata ceramic shock sensors:
http://www.farnell.com/datasheets/58860.pdf
http://www1.futureelectronics.com/doc/MURATA/PKGS-00LD-R.pdf

 

[Franc Zabkar]

Why are some drives designed to handle 2 free fall sensors?

Here are photos of Seagate's Momentus XT PCB:
http://www.storagereview.com/images/XT_PCB_TOP_large.jpg
http://www.storagereview.com/images/XT_pcb_bot_large.jpg

There is a white shock sensor located near the mounting hole at one
corner of the Winbond SDRAM. This sensor is mounted at 45 degrees so
as to respond to vibration in both X and Y axes.

There is a second vacant 14-pin location to the right of pins 1 and 2
of the SATA power connector. This unpopulated spot appears to be
reserved for a triaxial accelerometer. The pinout appears to match the
KXPB5 Tri-axis Accelerometer made by Kionix.

Here is a Toshiba MK5055GSXF laptop drive with the same accelerometer:
http://forum.hddguru.com/toshiba-mk5055gsxf-hdd2h71-500gb-apple-hdd-t17666.html

The drive has an additional shock sensor at location E2 near the
TLS2505 motor controller. It is mounted at 45 degrees.

Seagate distinguishes its free-fall sensor equipped laptop HDDs by
using an "ASG" model number suffix. There appears to be no difference
in the firmware of the AS and ASG versions.

Here is a comparison of the files in Dell's firmware update packages
for the Momentus 7200.4 models:
http://www.users.on.net/~fzabkar/Dell_AS_ASG_FW.jpg

R250352 is the update for the ASG drives, whereas R250679 is intended
for the AS versions.

The CRCs for each file are identical, as are their file names.

This update matrix shows that the same firmware image is used for both
versions:
http://www.users.on.net/~fzabkar/dell_fw_cfg.txt

- Franc Zabkar

 

[Franc Zabkar]

That would make sense and explain the two sensors. As the
platter spin in one plane, two sensors would cover platter
vibrations.

Here is one design that puzzles me:

Seagate 3TB Barracuda XT Review (ST33000651AS):
http://www.storagereview.com/seagate_3tb_barracuda_xt_review_st33000651as

The board has two shock sensors mounted lengthwise across the drive,
and what looks to be a third shock sensor mounted at 45 degrees near
the mounting hole above MCU.

I have seen other drives with similar arrangements.

Why lengthwise? Why not left-to-right and front-to-back?

And why do some drives have shock sensors that are mounted at some
other angle, eg 30 degrees or thereabouts?

- Franc Zabkar

 

[larry moe 'n curly]

Are you referring to standard shock sensors, or tri-axis
accelerometers?

I have no idea.

Typical shock sensors are mounted at a 45 degree angle in order to
detect vibration in both horizontal axes. The outputs from these
sensors are used to provide a compensation signal which is injected
into the voice coil servo control loop. Often there will be an
associated dual op-amp to buffer and amplify the signal. Otherwise
this circuitry is internal to the motor controller.

The tri-axis accelerometer detects movement in three axes. It is this
component that provides the free-fall detection capability. AIUI, it
is usually implemented as an all-in-one IC, rather than as a discrete
sensor with external signal conditioning circuitry.

Here is a review of Samsung's Spinpoint F4EG (HD204UI):
http://www.storagereview.com/samsung_spinpoint_f4eg_review_hd204ui

I can see three shock sensors in this photo:
http://www.storagereview.com/images/samsung-f4eg-pcb-top.jpg

There is one white device to the right of the Samsung SDRAM, a second
similar device at about 11 o'clock to the SH6125B motor controller IC,
and a third, smaller device above that same IC.

My HD204UI has only the third device. It was made in Oct., 2010, and
the circuit board pattern looks identical.

 

[Arno]

On 10 Jul 2011 11:54:05 GMT, Arno <[email protected]> put finger to
keyboard and composed:

Here is one design that puzzles me:

Seagate 3TB Barracuda XT Review (ST33000651AS):
http://www.storagereview.com/seagate_3tb_barracuda_xt_review_st33000651as

The board has two shock sensors mounted lengthwise across the drive,
and what looks to be a third shock sensor mounted at 45 degrees near
the mounting hole above MCU.

I have seen other drives with similar arrangements.

Why lengthwise? Why not left-to-right and front-to-back?

And why do some drives have shock sensors that are mounted at some
other angle, eg 30 degrees or thereabouts?

Well for this Seagate, I would conclude they are measuring
vibration at or close to mounting points. Having two of them
makes only sense for vertical vibration, as FR4 PCBs are
very stiff horizontally.

I noted that these two sensors are at 180 degrees to each other.
Maybe they are 2-axes sensors? But even then, you could not
cleanly identify 2-axes, as you only get 2 signals. Maybe
some half-baked differential setup.

Looking at some datasheets, these can be have their primary
axis horizontally, vertically and at some angle between,
e.g. 25 degrees. If these two are not the same, that could make
sense.

Arno

 

[John Turco]

These are acceleration sensors and have axes. If you only
use a 1-axis acceleration sensor, you can only detect a fall
in one direction. I would expect that is along the spin-axis
of the disk, that being the most sensitive and the way the
computer is typically oriended with regard to gravity.

Now, the thing these acceleration sensors detect duting
a fall, is the absence of gravity. If you orient the disk
vertically, a sensor designed to detect a fall when oriented
horizontally will not detect gravity and will not detect
a fall.

Anyways, these devices can detect a clean fall and
retract the heads. Thay are more limited on short falls
(e.g. 5cm onto hard desktop) and additional mechanical
buffering is needed in any case. I have no numbers, but
my WAG is that you get a surviving harddrive in 50%-80% of
the cases were a fall killed it earlier.

Now, there are 3-axis sensors on the market, that do not
suffer this limitation. I have no idea what using 2 sensors
accomplishes and suspect using one 3-axix sensor is cheaper
than using 2 1-axis sensors. Also I found a 3-axis sensor
at a 1-pice end-user price of about 4EUR, which indicates
these are not expensive in the first place. The 2 sensors
may just be a marketing stunt. Or maybe you can get 1-axis
sensors extremely cheap.

Arno

In September of 2008, I purchased two Samsung 500GB SATA
hard disks (HD501LJ), for a new computer build. Alas, I
soon dropped one of the pair, which took a fall of about
two feet. It ended up on a carpeted wood floor, but it
hit part of the steel frame of my bed, first.

Do you think any real harm was done? I never installed
either drive, and have since bought a duo of Samsung
1TB models (HD103SJ), in January 2011.

Anyway, I'd still like to use the HD501LJ puppies,
somewhere...it's simply that lingering doubts over
possible damage, tend to stop me.

 

[Arno]

In September of 2008, I purchased two Samsung 500GB SATA
hard disks (HD501LJ), for a new computer build. Alas, I
soon dropped one of the pair, which took a fall of about
two feet. It ended up on a carpeted wood floor, but it
hit part of the steel frame of my bed, first.

Not good. Steel is like dropping it on stone.

Do you think any real harm was done? I never installed
either drive, and have since bought a duo of Samsung
1TB models (HD103SJ), in January 2011.

Anyway, I'd still like to use the HD501LJ puppies,
somewhere...it's simply that lingering doubts over
possible damage, tend to stop me.

I would not trust this drive. I once had a shipment
of 10 inadequately packed Maxtors that were dropped
in shipping. 2 DOA, 1 with immediately recognized
damage, 2 more that died after 3 and 6 months.

I also droped a 500GB drive in an enclosure from about
1 meter (roughly 1 yard for the metrically challenged ;-)
onto a thick carpet. I could get all data off, but
the disk was nowhere full and reallocated sectors did
increase fast.

Arno

 

[John Turco]

Not good. Steel is like dropping it on stone.



I would not trust this drive. I once had a shipment
of 10 inadequately packed Maxtors that were dropped
in shipping. 2 DOA, 1 with immediately recognized
damage, 2 more that died after 3 and 6 months.

I also droped a 500GB drive in an enclosure from about
1 meter (roughly 1 yard for the metrically challenged ;-)
onto a thick carpet. I could get all data off, but
the disk was nowhere full and reallocated sectors did
increase fast.

Arno

Aw, rats! That's $70.04 USD, down the drain; I wasn't
very optimistic, anyway.

Oh, well...my plunked HD501LJ will make a unique (and
expensive) paperweight, no?

 

[Rod Speed]

John Turco wrote

Arno wrote

Aw, rats! That's $70.04 USD, down the drain; I wasn't very optimistic, anyway.

Oh, well...my plunked HD501LJ will make a unique (and
expensive) paperweight, no?

You could try using it and make a warranty claim if it dies.

They arent likely to be able to work out what happened to it
unless the steel of the bed left some visible damage.

 

[John Turco]

You could try using it and make a warranty claim if it dies.

After nearly three years? (It's an OEM drive, by the way.)

They arent likely to be able to work out what happened to
it unless the steel of the bed left some visible damage.

There are no obvious blemishes, as the steel was covered
by bed sheets.

 

[Rod Speed]

John Turco wrote

Rod Speed wrote

After nearly three years?

Yes, they have a 3 year warranty.

(It's an OEM drive, by the way.)

Not clear if the detail has changed with the Seagate buy out.

There are no obvious blemishes, as the steel was covered by bed sheets.

OK, I'd try it if it was mine.

 

[John Turco]

Yes, they have a 3 year warranty.

Correct, as my subsequent "Googling" has shown.

Not clear if the detail has changed with the Seagate buy out.


OK, I'd try it if it was mine.

No, I've decided that would be wrong. My own clumsiness
was responsible for the issue, of couse; Samsung can't
be held responsible, in any way.

Besides, it would be extremely hyopcritical of me...as
I've already mentioned it publicly, here on Usenet.

In any case (pun intended), I just may be lucky and my
questionable HD501LJ is actually fine! (I'll test it,
eventually.)