
Recover HD Using a Magnet - lrizzo
http://info.iet.unipi.it/~luigi/recover-hd/text.html
======
rgj
My anecdote:

Around 1993 I had a Commodore Amiga with an A590 external hard drive. A big
enclosure that could be connected to the expansion port on the left of an
Amiga 500, containing a very precious 20MB hard disk.

One day, it stopped working. I tried everything but I couldn’t get it to work.
A friend offered to take a look at it so I put it in my backpack and took the
train to my friend. When connected to his A500, the drive worked lime a charm.

When I drove back home in the train I wondered what would be the matter with
my A500 since it apparently made my A590 hard drive fail.

However, once I got home and reconnected the drive, it worked. No problem
whatsoever.

Until two days later. It failed. You know what’s going to happen, right? Took
it to my friend, it worked, took it back and it worked for two more days.

Turns out that disconnecting it, putting it in my bag, walking it around for a
while worked just as well.

Turns out that disconnecting it, dropping it from 5cm / 2 inches and
reconnecting it, worked just as well.

Which was what I did for the next four years or so. Whenever it stopped
working, I disconnected it, dropped it and reconnected it.

Always loved the look on the face of people who witnessed me starting up my
Amiga.

~~~
ChuckMcM
FWIW the failure mode (which was also common in drives for the SPARCStation at
the time) was called "stiction." That occurred when the drive parked the
heads, after power down, into the landing zone on the platter.

At Sun we took apart a number of failed drives (which could also be recovered
sometimes by giving them a sharp twist) and hunted for the root cause. The
answer was that over some time the drive heads became smoother and the surface
of the landing zone also became smoother. When the tiny edges of the head had
been removed by this process, the surface of the head was pretty much
optically smooth (very little variation) and when it landed in a part of the
landing zone that was similarly smooth the surfaces would push out the air
between them and become stuck just by air pressure and surface friction
(stiction). The drive would not spin up until the head had lifted off the
surface. The firmware issue was that head lift off was checked for so quickly
that the power up of the spindle was aborted before anything happened (this
was to prevent damage to the head by dragging it along the platter's landing
zone). By jostling the drive you could manually cause the platters to rotate
and if you found a spot that wasn't completely smooth (or if you managed to
have the heads move out of the landing zone) the surface would be rough enough
that the head wasn't being held down and it could lift off again.

Seagate gave us a firmware fix which basically waited longer for the heads to
lift off allowing the spindle motor to move the platter a bit before giving
up. Quantum (the other disk supplier) beefed up the retract solenoid and gave
us firmware that would try 'regular' retract and then 'heavy' retract before
giving up. For a pretty long time I had a Seagate drive that had been
disassembled to the point of exposing the heads and platters so that the
effect could be demonstrated to skeptical engineers.

~~~
foobarian
An IBM tech told me how they sometimes resuscitated drives that wouldn't come
up after power cycling. They would spin the drive on the floor for a few
seconds and then quickly hooked it back up before the platters stopped moving.

------
glennvtx
I have fixed a ton of drives, in general. Board replacements, swapping
platters, head swaps, etc. Some takeaways: I started doing this under
tupperware, and that worked. I built a "cleanroom" out of a new sandblasting
cabinet, and that worked better. Later i built a laminar flow bench out of a
cheap kobalt tool-box and some plexiglass, and that was better still.

Swapping the control boards works on some makes (wd), make certain it is
exactly the same model and revision. exactly. "close enough" never worked for
me, not even once.

By far just a slight "spin" by hand along the axis of travel of the disk, a
quick gentile flicking motion, works to unfreeze the spindles of most stuck
drives.

Some drives responded to a gentle heating of the spindle bearing with the hot
air.

Use dd_rescue.

"Spinrite" is complete horse-shit, don't listen to anyone saying otherwise.

Most drives people brought in were just corruptions, photorec and it's
associated programs (testdisk) are also invaluable..

~~~
eitland
Do you (or anyone else) have ideas for what to do with

\- a MyBook that isn't recognized anymore?

I've figured out there's probably some encryption in the casing because when I
disassemble it and connect it directly it shows up as unformatted or
something.

\- an ssd which seems even more dead.

Personally I've gotten back erased data (photorec) and data from at least 2
other disks (tilting the disk or freezing the disk), but these two have me
stumped which is sad since they broke shortly after each other and one were
supposed to be the backup ;-)

~~~
londons_explore
The drive itself is likely good - it's probably a software/config error with
the casing. A drive recovery company will probably be able to recover it
cheaply, or third party recovery software on the bare drive.

~~~
eitland
Ok, thanks!

Would you happen to know why they'd transform the data instead of just writing
through?

Oh: and I also added detail about another drive to my question. I didn't think
anyone would answer that fast :-)

~~~
londons_explore
Normally they shift all your data a few hundred megabytes later in the drive
so they can use the area at the start to store their "drivers" (ie. The
software they encourage you to install on your PC to offer backups,
encryption, cloud storage, antivirus, and other crapware of dubious value).
Sometimes the casing firmware emulates a CD-ROM device and offers this data
because the OS will autorun software from a CD. Then when the software is
installed, it switches to hard disk mode to present your actual data.

The external drives which offer 'encryption' nearly all do it through software
on the host PC and sometimes the drives built in encryption (did you know all
modern hard drives can encrypt data before writing it to the platters? -
nobody uses it because you can't tell if the drive really is encrypting your
data or just pretending to).

~~~
eitland
> Normally they shift all your data a few hundred megabytes later in the drive
> so they can use the area at the start to store their "drivers"

So, if I'm really lucky I can use testdisk to find the partitions and just
mount it read only from there without involving a recovery company?

~~~
londons_explore
Yep. As soon as you find the sector number of the start of your data, you can
use "losetup --offset xxxxx" to use it like a regular disk again. I think
there are even SCSI commands you could send to permanently shift the start of
the disk. Or you could just dd all your data back to where it ought to be.

~~~
eitland
I read a bit more and it seems some models has encryption mode (by default
using an empty string for a password it seems.) There exist at least two
projects to get data from those MyBooks so I'll try those if the simple
version doesn't work.

------
bewilderbeast
My story:

In 1996 or 97, a friend brought me his Compaq Deskpro, the SCSI HDD had
stopped working. No sound at all, dead. Tried everything, checked voltages,
reconnected cables trying to clear any oxidation. Wouldn't spin at all. Well,
called it a night.

Next day, decided to take it out of the chassis for a last test, connected
outside. Not only it spun, it worked fine!!! WTH????

Well, into the chassis it went. Nothing. Dead. Whaa..??? Outside again, it
worked. In the chassis, dead. Outside, worked. Scratched my head... With it
working outside, just tried to place it on top of the chassis. It spun down
and stopped. Took it away, it spun up. Got it close again to the chassis, it
spun down again... Scratched my head again... Gave up, left it disconnected
outside for the day.

Next day tried it again and this time it worked outside of and in the
chassis... My thoughts? The chassis was magnetized or something...

Worked for a couple more years.

~~~
0xcde4c3db
Perhaps a defect in a cable or connector such as a broken wire or a dry solder
joint? These often cause problems that mysteriously appear or disappear as the
cable is moved and the changing forces on the defect make and break the
connection.

~~~
bewilderbeast
Nope, I tried everything, twisted the cables, etc. I even changed from power
connector to another and changed SCSI cable. Outside it worked, inside didn't.
Working perfectly outside, as soon it got close to the metal of the chassis it
spun down, and as it got away from the metal it spun up.

------
dukoid
Don't use dd -- use ddrescue (reads all "working" sectors before retrying
broken ones).

~~~
ddtaylor
Does this mean it puts less strain on a potentially broken disk in an attempt
to maximize how much can be rescued before it fails?

~~~
askvictor
yep; it's quite clever about how it deals with broken sectors too; starts
jumping over them in increasingly large amounts, and goes back later (in
multi-pass) to get the missing bits.

------
tyingq
If you Google for the word "sticktion" or "stiction" you'll find other
remedies. Like putting it in a ziplock bag and freezing it, or (youch)
purposefully dropping it.

All approaches to release a head that's stuck to a platter.

------
sdfjkl
I've fixed this problem a few times (on different drives) by giving the drive
a not so gentle thwack with a hammer. The trick is to hit it on the long side,
which tends to dislodge the stuck heads/arm. If you hit it on the top or
bottom, you're likely to break something, and hits on the short side aren't
likely to achieve anything at all.

~~~
LIV2
Many jobs ago we had an outage caused by 2 drive failures in a Raid 5 system,
that was resolved by banging the drives on the ground a couple of times before
putting them back in.

If I still worked with physical servers I'd be carrying around a rubber mallet
to apply "percussive maintenance"

------
azinman2
How did the data not get destroyed by the magnet?

~~~
cecja
the whole magnet and hard drives thing is a really old hoax. with normal
household magnets or even strong neodym magnets nothing will happen to your
data but if you have a really strong industrial electro magnet at hand you can
wipe a drive with it...

here is an old national geographics video on the topic
[https://www.youtube.com/watch?v=U8LWTe5CqQg](https://www.youtube.com/watch?v=U8LWTe5CqQg)

~~~
EvanAnderson
Here's my anecdote:

In 2006, while sitting at my desk playing a video on the Travelstar 40GB PATA
drive in my Thinkpad T22, I held a single neodymium magnet (harvested from an
old hard disk drive) about 6 inches from the left side of the unit (where the
~disk was located). The video froze, Windows XP blue-screened, and the hard
disk drive started emitting a ~10Khz whine. I jerked my hand away from the PC
immediately when the whine started

BIOS would no longer detect the disk on that machine, or any other I tried it
on (on both USB-to-PATA and honest-to-goodness motherboard PATA controllers).
The drive spun up but made a repeated ticking sound (I assume seeking back and
forth looking for servo tracks).

I sent the drive to Kroll Ontrack (because, stupidly, I had billing data that
wasn't backed-up on the drive). The report I received back indicated that 80%
of the drive's sectors were unreadable.

As an aside: The data I was looking for was ASCII text and Kroll Ontrack was
completely unhelpful in just sending me a bitstream image of the drive so I
could grovel thru looking for data I needed. Being plain ASCII, their "file
carving" tools didn't locate any of the data. (They sent me a "preview" of the
data they'd located, and while it got lots of Microsoft Office-format files,
it didn't have any ASCII text files). I offered them a 3x multiple of the rate
they asked for file-level recovery to simply send me the bitstream image of
the disk that they'd already made. They wouldn't do it, and wouldn't even let
me pay to talk to somebody who understood what I was asking for. I ended up
taking a major loss on the billing data I destroyed. I'll never recommend them
to anybody.

I won't ever play with neodymium magnets around spinning rust media again
either. I also had a major failure of my discipline re: backup at that time,
too. The cobbler's children always go barefoot-- I was being too cavalier with
my backup strategy (or lack thereof) and not treating my own data like I would
a Customer's.

~~~
egdod
Sounds like a coincidence.

~~~
EvanAnderson
It does sound that way but, boy, it was eerily timed if it was.

~~~
mlyle
Magnetic field falls off with inverse cube of distance once you're past the
approximate size of the magnet. Not to mention that the drive itself is in a
ferrous enclosure that provides a lot of shielding... the magnetic field you
applied at 6 inches is approximately nothing.

~~~
FabHK
Isn't it inverse square?

~~~
mlyle
No. Magnetic fields fall off as 1/d when d is small compared to the size of
the magnet, progressing to 1/d^3 when d is large compared to the magnet. (E.g.
weird edge case-- it's inversely proportional to distance from an infinitely
long wire).

Electromagnetic radiation from point sources falls off as 1/d^2.

~~~
FabHK
Thanks a lot, both of you, learned something!

------
randompi
View page source. What a beauty ️️.

~~~
thepete2
Really? He doesn't close the <p> tags.

~~~
wizzwizz4
That's only a problem for XHTML. HTML5 implicitly closes the previous <p> tag
when you open the next one; thus, a <p> inside a <p> is an implicit </p><p>,
if you will.

~~~
colejohnson66
Why does VS Code auto add the closing <p> tag when you open them then? It
doesn’t do it for, say, <img>. Bug?

~~~
wizzwizz4
Feature. <p> tags can function as containers for text and other elements, and
VS Code can't distinguish between <p>, with the special handling, and <div>,
without it.

Okay, to be fair, that _does_ sound like a bug.

------
jacquesm
Clever! I'm stuck on a problem right now as well, I'm trying to boot an old
server (Supermicro, dual CPU) to verify something and for the life of me I
can't figure out what is wrong with it. It doesn't do _anything_ when you
power it up, even the power led on the board doesn't light up. Forcing the
powersupply to 'on' does light up the LED but the system still won't boot.
Already put a fresh 3V cell in it, stripped it down to the bare minimum, all
jumpers in default positions, no go. And it worked perfectly fine the last
time it was shut down. Highly frustrating these gremlins.

~~~
lallysingh
Oh, did any caps blow? There were some counterfeit ones going around some time
ago...

~~~
jacquesm
That's a good one, did not think to check that, I'll go over all the caps on
the MB.

------
throwaway3563
The strangest HDD failure I ever dealt with was a Toshiba notebook drive where
the centre bearing had become shot. The notebook would not boot and the HDD
sounded like a coffee grinder.

By moving the notebook in the air and trying different positions the noise
changed. I was able to get the machine to eventually boot by holding the
notebook in my hands at an angle and spinning myself on the spot. At the time
I guess the gyroscopic forces were enough to get the bearing to sit right and
the HDD to be able to spin properly. Doing so caused the drive to work long
enough to get the most important files off it.

Definitely the strangest thing I’ve ever done to “fix” a piece of computing
equipment.

------
djsumdog
I have successfully used the freezer trick a few times to recover a hard
drive. It did work in those instances and I documented it here:

[https://battlepenguin.com/tech/freezing-a-hard-
drive/](https://battlepenguin.com/tech/freezing-a-hard-drive/)

If you can, leave the hard drive in the freezer while you access it. Only
works for old spinny hard drives of course.

------
tartoran
I had numerous HDs fail with the clicky noise when powered up. I was never
able to recover any of them. Is it possible nowadays to fix these without
replacing the drive controller? I remember this clicky problem forever
destroyed my trust in harddrives. Are hard drives any better these days??

------
vectorEQ
instead of magnet, what i used to do with ticking / corrupted drives was write
full of 0, then write full of 1, then full of 0, repeat a few times. it takes
frigging agents, but it kind of gets out all of the bumps in the magnetic
material and smoothens it out again. fixed many broken drives doing that.
ticking is often the read head getting dumped too much due to magnetic
substance on the disk being piled up too much giving too much of a push to it.
then the ticking will cause similar piles to form and get worse and worse.

~~~
londons_explore
Alternative explanation: some sectors are unreadable due to checksum errors
(caused by improper powerdown). Repeated read requests sounds like ticking
because the head will be seeked every time.

Writing all 1's or 0's to the drive causes those sectors to either be
rewritten or reallocated.

The fact it's 1's and 0's wouldn't have an impact anyway - all drives use data
whitening techniques anyway.

------
unnouinceput
Those $1.5 apparently came from a leprechaun, there is no other explanation
:).

------
wwright
This a fantastic webpage.

~~~
djsumdog
Simple and straight to the point ... although some navigation would be helpful
to see, you know, the rest of the website.

~~~
knolax
TBF from the ~luigi part of the url you can tell that it's probably one of
those "web sites" allotted to each user on a university server or something
similar, eg. go to
[http://info.iet.unipi.it/~luigi/](http://info.iet.unipi.it/~luigi/) for his
homepage.

