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Write Bits Directly Onto a Hard Drive Platter?
kidcharles writes "I'm working on a project that requires writing bits to a magnetic hard drive platter in a completely controlled fashion. I need to be able to control exactly where 1s and 0s will appear physically on the platter. Normally when data is written to a drive the actual bits that get written are determined by the file system being used, as modified by whatever kind of error handling the drive itself is using (e.g. Reed-Solomon). All of the modern innovations in file systems and error handling are great for reliable and efficient data storage, but they are making my particular task quite daunting. My question for Slashdot: is there a way to get down to the 'bare metal' and write these bits? Any good utilities out there to do this? Obviously a free and open source solution would be preferable, but I'm open to anything at this point."
It works for me. http://www.staples.com/Staples-Dry-Erase-Markers-Chisel-Tip-Black-4-Pack/product_607101?cmArea=FEATURED:SC1:CG11:DP1101 Now that someone has said it no one else can be a smart ass and they have to be informative.
Just make your own controller chip for the drive.
You would need to replace the firmware inside the drive or use an undocumented manufacturer mode. Whatever they use to write the servo tracks would be interesting to you. You will be in the situation of the firmware writer: There will be problems all the way. Be prepared to find a way to position the heads (ever tried to find a servo track?). Most likely you also need to at least parametrize the amplifiers in the DSP part of the firmware that does the analog-to-something-to-digital so you can have direct influence on the "bits". Good luck
The submitter appears to know enough about what he's asking to know that it's also impossible / completely impractical. Recording ones and zeros directly isn't done for a reason, submitter appears to understand this.
Your requirements are wrong, sorry.
Yes, I don't what they are. Still wrong.
I can't help directly, but can give one important advice - careful how you distribute the bits! If too many ones get on the same side of the platter this will destabilize it, causing it to wobble due to the weight difference ( a one weighs quite a bit more than a zero, you know!) and potentially tearing the platter in two!
This kind of copy protection has been outdated for quite some while and should have died with floppy disks ...
These kinds of questions are stupid: "I need to do XYZ for a project, how do I do XYZ?", where XYZ is one or more of complicated, ridiculous, vague, nonsensical, etc. Try telling us what your project is, and then we might be able to suggest a useful solution, possibly not involving XYZ at all, or involving a very particular/practical version of XYZ.
"I'm working on a project to build a nuclear powerplant. Is there documentation on how to do it? Obviously a free and open source solution would be preferable, but I'm open to anything at this point."
It seems to me that if you're involved in such a project and have to ask how to do it, it's doomed.
Also, the whole idea of it seems rather impossible. Why would you want to do this in the first place? Have in mind that hard disks don't write bits as is, not just because of ECC. They use an encoding to ensure that there are no long strings of 1s or 0s. If you just wrote some data without regards to that you'd run into a sequence you'd be unable to read later, due to not having a clock signal to figure out where a bit ends and the next begins.
Modern hard disks require using special encodings and servo data in order to be readable at those densities. It just makes little sense to me to want to bypass it. Unless you're working for a disk manufacturer this just seems very odd, but in that case you'd have access to the required equipment and information.
I'm actually more interested in why the fuck he wants to do this, much less how it would be achieved.
The stuff Spinrite does stopped working 15 years ago. On modern drives you're pretty much doomed. Considering Gibson has been known to rip off SYN cookies and spout such nonsense as "Windows RAW sockets are going to destroy the internet", I wouldn't go anywhere near him for advice.
Got myself a disk editor, and wrote something on the very first sector.
After that I can't use the HD anymore.
The computer can't even recognize it anymore.
Muchas Gracias, Señor Edward Snowden !
Short answer: no, it's not possible to do that. It's not impossible, simply incredibly hard to do. Unless you happen to be very handy with a soldering iron and go dumpster-diving in the backyard of an HDD company (as many others have pointed out).
Longer answer: how about creating a 'virtual' hard drive? There are utilities out there that probably let you create (a) a virtual interface (let's say IDE) and (b) a virtual hard drive, attached to said interface. The next step, of course, is to hack these (VirtualBox?) in order to make them do whatever it is you want them to do. This being said, I strongly suspect it involves non-trivial virtual machine hacking and that it probably does not respond to whatever your needs are.
Other than this (very twisted) idea, sorry, bare metal writing has been disabled a long time ago, and for good reasons, too.
The right to offend is far more important than the right not to be offended. (Rowan Atkinson)
Old MFM hard drive should do the work. The entire device was controlled via software in dos. I have one lying around. A whopping 5 MB!
http://en.wikipedia.org/wiki/Modified_Frequency_Modulation
Now all you need is a 8 bit ISA slot and you are set.
RES PUBLICA NON DOMINETUR
The cynic in me wonders if he is working for some hack start-up company trying to develop a DRM scheme for a hard drive, similar to the crap the studios do to DVD's to make them difficult to rip. Typically this involves creating some sort of currupt/invalid area on the disk that your particular device will know to ignore, but will lock up anyone else trying to read the data off the drive.
The optimist in me wonders if he is trying to defeat such a scheme.
It can not be done with off-the shelf equipment and software for many reasons, some of which are:
Line Codes
Error Correcting Codes
PRML
SMART
LBA
etc.
Specialist Mac support for creative pros, Melbourne
We don't need to work like that any more.
Get yourself an old, totally unintelligent S412/506 MFM controller from out of an IBM PC or PC/XT. These were fairly dumb devices (g=c800:5 in debug, anyone?) for which you were meant to enter a "bad sectors list" printed on the front of the drive after performing the low-level format yourself. The earlier the drive, the closer to bare metal, so you might want to look for any of the 2, 5, or 10MB (yes, MB) full-height (2 x 5.25" drive bays stacked on top of one another) drives that were floating around then. You'll also want to get yourself a set of ribbon cables.
You should be able to use a drive/controller combination like this with any machine with ISA bus slots up through about the 386/486 era, and that would let you also go back and grab an early Linux distro (say, kernel 1.2.13 days, like Slackware 3 or so) that included drivers for such a controller that were actually in use and known to work at the time, giving you a base on which to build more code.
If 10MB is too small, you might just have luck going up to the largest of the MFM (80MB) or even RLL drives (160-200MB, just get an RLL controller instead) drives. I don't remember whether there were any ESDI drives back in the day that didn't remap their own sectors, but if there were, these controllers were 16-bit ISA and somewhat smarter (also with Linux drivers from the period available) and went up to 680MB or so.
But if you're looking for the best chance of success for your purposes and don't need tons of storage, my educated guess would be that the MFM controller out of an IBM 5150 PC plugged into a 5MB ST506 hard drive and connected to a SIMM-based 80386DX mainboard with 8 SIMM slots (for 8MB ram) might be the easiest combo to find and get working in practical terms that has a chance of doing what you want.
STOP . AMERICA . NOW
I think anything > 120MB may be unsuitable for this purpose, as they are likely to use ZBR, i.e. different sector densities depending on the circumference of the track. I'd also recommend a really old MFM or RLL disk, where the head movement is controlled with one set of wires and the analog signals from the read/write heads use another set of wires. MFM and RLL drives use the ST506 interface, which should be "easy" to control with microcontroller and a little bit of glue logic.
And if he's trying to see if he can read data patterns off platters by hand from a dismantled drive, and needs a known test pattern to calibrate his equipment with?
I'm working on a project that requires writing protons to an atom nucleus in a completely controlled fashion. I need to be able to control exactly where protons will appear physically on the nucleus. Normally when atoms are created during fusion the actual atoms that get created are determined by the energy input of the fusion reaction as modified by whatever kind of atoms are being fused (e.g. hydrogen into helium). All of the modern innovations in nucleosynthesis and alchemy are great for particle colliders and crackpots from the Middle Ages, but they are making my particular task quite daunting. My question for Slashdot: is there a way to get down to the 'bare metal' and transmute lead into gold in a cost-effective manner? Any good utilities out there to do this? Obviously a free and open source solution would be preferable, but I'm open to anything at this point.
Finally had enough. Come see us over at https://soylentnews.org/
You know how data restoration companies do it?
They take out the spindle with the platters, and put it in their own reading device with its own controller. And with that you can read and write the exact bits (as long as quantum physics allow it). But the head has to be compatible (e.g. perpendicular recording needs entirely different heads).
I bet those devices can be bought, and I bet their controller is actually just software on the computer (for flexibility). I also bet they come with different head configurations.
But they are definitely not going to be cheap.
Hey, at least it is a real solution. :)
Any sufficiently advanced intelligence is indistinguishable from stupidity.
"I'm working on a project that requires writing bits to a magnetic hard drive platter in a completely controlled fashion."
Are you sure?
The reason I ask is I'm working on a project that requires me to move data faster than light. At least that's what I spent last Monday working up the math to prove that data replication between our different data centers has an upper bound enforced by the fabric of the universe and that it was impossible for me to achieve the project's stated goals without essentially inventing warp drive. As it turns out after a meeting it was determined that the goal was just a stated guideline. It also turns out the price of faster data transfer rates is prohibitive and after a further meeting the stated project goal was total baloney. Yes. Baloney. We had sandwiches. It was a nice meeting.
[signature]
Don't you hate it when people refuse to accept the premise of a technical question and write long monologues why the submitter is working with false assumptions even though they don't know what exactly they are dealing with? Yeah, me too. Makes them look arrogant, ignorant and smug. I'm going to go ahead though and reject the submitter's premise: there is no chance in hell that you're on the right track with whatever project you're attempting to do. But instead of merely dissing you for incompetence, I'll lay out a few scenarios (might as well, since you didn't supply any of your own).
If the actual physical bits matter to you...
you're either a hard drive manufacturer or a clueless person who should read up on how drives actually work. And we both know you're not working for a manufacturer. What you need to know is that there are several layers of indirection between the write call from within an OS down to the actual magnetic platter. These layers are there for a reason. At the very least, the onboard controller of the drive abstracts away the physical block allocation, and the drive won't work without the controller at all. Since the intricacies of the drive's physical address space are not accessible from the outside, there will never never never be a reason to try and fiddle with it directly. Because you can't.
If you are looking for disk I/O without a filesystem...
we're finally in saner territory. There are valid reasons to do this, e.g. speed and overhead considerations. Some database vendors actually have features like these. In this scenario, you're using the entire drive as one big addressable blob. A good starting point would be to have a look at the source code of a simple filesystem, such as ext2. Strip away all the actual file handling stuff and learn what you can from the disk I/O routines. On the other hand, if you didn't arrive at this conclusion yourself, that's not a very encouraging sign.
If you simply want a drive without error correction...
you're not developing software that will run on any modern system. If you accept this caveat, you can buy an ancient drive off ebay and use that. However, keep the first scenario firmly in mind: there is simply no reason to control the exact placement of every single byte if you don't plan on literally putting the drive under a microscope afterwards. Otherwise, this has no practical implications and, again, you are on the wrong track.
If you're a DRM/malware/virus developer...
I will sleep very comfortably tonight, because you had to ask about this on Slashdot, signaling once more that you're doing it wrong.
I'm surprised by the number of people who seem hostile to this question, mostly because they can't imagine any circumstances where they would want to do this. I can think of several. In fact, I was thinking about something similar with optical disks just earlier today. (I'm curious whether small holograms could be created by writing an interference pattern directly onto a CD or DVD, but I would need exact control over how the tracks lined up to achieve this.)
Here's some concepts just off the top of my head:
* He's come up with a new disk encoding scheme, and wants to try it out.
* He's doing research into how long disks retain data, and is questioning basic assumptions like whether surface bits permanently magnetize the platter underneath, affecting later bits in the same location. Or how far the domains spread.
* He's working with self-assembling molecules and needs to give them a patterned magnetic surface to build on.
* He wants to 'print' a 2-D picture onto a small portion of the hard drive, and bounce a laser off it. (The magnetic alignment of the surface domains would polarize the photons slightly.)
* He's making a high-resolution rotational position encoder, so by reading across 32 tracks knows the rotation of the platter down to a few nanoarcminutes.
* He wants to totally destroy the contents of a disk. (I assume this is what most of the hostile people think is the intention, presumably as the payload of some virus)
Those are just the ones off the top of my head.
However, the ranting people do have a point that without knowing WHY you want to do this, we can't really suggest the best solutions. A lot of people have recommended going back to super-old MFM hard drives that allowed this, but we don't know if you require the density of modern hard drives.
To do this with a modern drive, you're basically going to have to rebuild the controller. Either totally remove the controller board (leaving handy raw connections to the stepper motors and drive heads) or cut the connections between the microcontroller and the low-level electrical functions of the drive, and substitute your own. Here's where knowing your accuracy requirements could have help, because if you want relatively large bits, you can get away with fairly low-frequency components. A 20Mhz microcontroller can, with say an external high-speed shift register, push out an 80mbit/s serial stream, which equates to >120,000 bits around the track of a 6,000RPM drive. Not quite the same density as the manufacturer, but better than the old MFM drives.
Your next problem is going to be this: It's really, really hard to tell where the head is on a platter. I've no idea how modern drives do it, but it used to be done with 'marker' bits either in the track, or on a nearby 'index' track, plus a little timing. Preserving these location marker bits is actually the most important job of the drive controller.
It's not impossible, merely very difficult. I could probably make one with only several weeks of hard work.
Alternately, you could try getting into the firmware and re-writing it to your specifications, but that might take longer. You would have to reverse-engineer a lot of stuff that is specifically hardened against this, but at least the hardware would be stable.
Jeremy Lee | Orinoco