As is well known, modern HDDs (think 4 to 8TB SAS/SATA) are low level formatted by the manufacturer before sale, ready to hold data. "Reformatting" usually just means clearing the user data content within the existing tracks/sectors (this includes wiping track 0, or "quick formatting").

Manufacturers allow download of tools for their drives (such as Seagate's "seatools"), which can do something described as "low level formatting", but its not at all clear to me if this is simply a "lower level reformat" or a true low-level format.

One reason for my doubt is that with modern drives, I'd be surprised if the original track write wasn't part of a larger process, where the data obtained is then fed into calibration and control parameters governing the details of head control for each platter and the unit as a whole, so that manufacturing variations in nanometer-scale electronics and head servos etc, or variations in the microcontroller or HDD firmware, result in internal parameters exactly suited to governing that specific drive. Also to improve yields, drives that are slightly sub-tolerance might have slightly different control parameters that don't push them so hard (so they can still be sold as intended). Furthermore because two PCBs for the same model may not be interchangeable so possibly the issues go deeper.

In which case perhaps the platters can be truly low level reformatted (because the physical components and parameters are unchanged once initially assessed/measured)... or perhaps they can't. Maybe rewriting the tracks would only make the drive's parameters suboptimal rather than unusable.

So my question is, can an end user these days truly low-level format a modern HDD? Meaning, rewrite the actual data tracks as if the disk platters were not already formatted and had no tracks or data whatsoever, and it works? I also mean realistically and outside a lab/production line - whether it can be done via software-only in a home or small-scale environment, is necessary software available that an average end-user would need. There's some "get-out" clauses I've got to mention, to make the question more focused:

  1. I'm assuming that any firmware/flasher encryption keys are a non-issue but they might be a serious obstacle in reality. Are they?

  2. I'm also assuming the user can pull off the PCB but doesn't have a clean room, and really doesn't want to dismantle anything if they can format using a software-only approach through usual SAS/SATA ports. The question is really about whether an ordinary person can realistically truly low-level reformat modern HDDs, not whether one can hack their innards to levels worthy of a DefCon paper :)

  3. I'm assuming that the user can (if they wish) control or rework the firmware flasher which means in theory if there's no other way, they can get the controller to do anything it's physically capable of doing, including any data write. (Assumes no insurmountable keying or dismantling issues). But perhaps the controller is physically incapable of reformatting outside OEM situations for some technical reason, or OEMs might burn a link in the chip itself before sale to prevent some actions. So there may be physical limits on some actions, and these might or might not block low level reformat.

  4. It could be the case that low level reformat is possible but not realistic, because you can't do it due to the callibration issue, unless you have some hardware or specialist equipment/parameter calculators that's needed, and which isn't realistic to obtain/access and there isn't a readily downloadable equivalent to reverse-engineer or replicate. In that case some businesses could do it commercially, with bundled control systems available to OEM partners, researchers and data recovery labs, but not really anyone else. That's useful to know but doesn't really say how far a person without those contacts and resources can go. It essentially says "yes, if you're able and willing to replicate the key part of the OEM production line to do it".

  5. Last, one might be unable to low level format as it stands because of the calibration/params issue, but could hack a simplified firmware or homebrew that doesn't rely on such highly tuned params, flash it, and do what they like on the platter. Again useful to know but I'm really thinking about a low level reformat that let's the drive be used afterwards with the standard manufacturer's firmware, ideally without affecting reliability much if at all.

Why might an end-user want to low level format? Most won't. I can think of three reasons, running from possible to esoteric:

  • An old drive is discovered, for some reason it seems to spin up but bit flips and degradation have somehow degraded the manufacturer low level tracks (but magically not the mechanism or EEPROM/NVRAM firmware/params), and the user is curious if it can have its tracks rewritten and if so, if it would then be usable again, as a kind of hobby/experiment.

  • The user wants to do something akin to old 1970-1980 era hobbyist floppy disk systems, where you wrote your own disk access code and stored data on the disk arbitrarily as you chose. The user has figured out the JTAG and microcontroller, or can unlock OEM functions or reprogram the firmware, they'd now like to know if the drive is physically capable of low level format and, if so, if they are stuck with the tracks the OEM laid down (and modifying inaccessible data within that pre-created track/sector structure only), or if they can rewrite low level from scratch.

  • The user is paranoid and/or works in very high sensitivity areas, and wants to low level format before use, in case the NSA has persuaded the major 2-3 drive manufacturers to add code buried in the low level format (skipped sectors, empty spaces etc). (As an aside this can be done, and in any case extended disk firmware, parameters, cache dumps on power loss, etc is routinely held on non-user areas of the drive as part of ordinary operation. So it's not entirely paranoiac). The user can access and check the firmware (see previous example) but wants to low-level reformat drives they buy before use, to ensure they know exactly what's stored rather than taking it on faith.

So - is this technically possible with modern HDD manufacturing approaches (for majors such as WD/Seagate/Toshiba), and to what extent is it possible?

  • Under the standard definition of end-user the anwser is NO. If you want to learn the JTAG interface and decrypt/decode the firmware. Then de-compiling it to source code. Learning how to program is the language it was written in and so-on. This is years worth of learning that no standard end-user would undertake. However, it could be done, eventually. – cybernard Jul 28 '17 at 18:03
  • If you want to go down that road that leads to mads read this article. malwaretech.com/2015/04/hard-disk-firmware-hacking-part-1.html – cybernard Jul 28 '17 at 18:10
  • There is a tool published by HDDGuru that claims to be able to low-level format a drive. – BillDOe Jul 28 '17 at 19:38
  • Note that on SCSI drivers, the answer is “yes” as the SCSI standard actually provides a low-level format command. Not sure if it does anything special on modern disks, but it surely does erase the whole damn thing. – FUZxxl Jul 17 '18 at 20:02

can an end user these days truly low-level format a modern HDD?

No, because there is no ATAPI command in current versions that provide such capability (e.g. there are essentially only sector write and read commands). Also there is no seek command anymore.
Since the actual drive geometry (numbers of cylinders, heads, and sectors per track) is no longer known by the user (or anybody/anything external to the drive), track format and explicit seek operations should not be performed.

For sure, "low-level" format (i.e. write the track with address marks, IDs, and gaps) disappeared when HDDs started using zoned-bit recording. The "low-level" format became an endangered command when IDE drives fixed the sector size to 512 bytes.

  • Good points. But perhaps the manufacturer makes the interface, or the other interface (some drives have extra pins next to the sata/sas port, or on the PCB) respond to both the ata command set and a separate manufacturers command set - after all, it would serve them to have access beyond that of the usual end-user set, for testing, troubleshooting etc. – Stilez Jul 28 '17 at 20:02
  • The end-user (or any OS and disk utility programmer) can only access the HDD through the ATAPI interface. The reasons for the removal of format and seek commands are simple, and don't involve esoteric "calibration and control parameters". Speculation on the existence of undocumented interfaces and their capabilities is off-topic for this site. – sawdust Jul 28 '17 at 22:18

Within the restrictions of a single computer and single user, no.


"If you have access to the hardware, you own the computer."

Sufficiently motivated, a user can remove a hard drive from a computer and place it in a different computer, and they'd be fully able to do anything they wished with the drive.

This is one of many reasons why encryption is such a basic part of security these days.


To overwrite all sectors in Windows, run the following commands (replacing 0 with the disk number):

select disk 0
clean all

From the help:

Syntax:  CLEAN [ALL]

ALL         Specifies that each and every byte\sector on the disk is set to
            zero, which completely deletes all data contained on the disk.
  • You haven't understood the question. What you're describing isn't a low-level format. A low level format (re)writes the actual tracks and sectors themselves, and perhaps their tracking/servo indicators too. What you're describing keeps those sectors as the manufacturer formatted them, and rewrites the data they contain. Low level formatting is when you physically set out the empty sectors themselves in the first place, on a completely blank platter that doesn't have sectors already, after manufacture/demagnetising. – Stilez Jul 28 '17 at 17:55
  • @Stilez If you somehow configured the drive's firmware so that it has no sectors, the drive would be non-functional. Is the purpose to have a non-functional disk? If you configured the drive's firmware to not have sectors, then have sectors again, you'd just be going in a circle. – Jason Jul 28 '17 at 18:00
  • Again, you're not understanding the question. Research a bit more what is involved in low level formatting - not wiping data, not making the disk unusable because it has no sectors, not going in a circle. – Stilez Jul 28 '17 at 19:17
  • @Stilez If you really want to get in a pissing match about understanding and research, you should know that "low level format" hasn't been a relevant term since before ATA was standardized in the early 90's. – Jason Jul 28 '17 at 19:29
  • Thanks. Doesn't mean it can't be done, but by who, and how, is what interests me here. Let's call and end to this thread , though. – Stilez Jul 28 '17 at 19:59

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