Left Handed Brisket wrote in post #18570025
If low level format writes zeros to everything (which is my understanding) that takes the typical recovery tools out of the discussion. They will be ineffective.
You then move to expensive professional level software. This software looks for "latent", for lack of a better term, evidence of a charge.
"Low-level formatting (i.e., closest to the hardware) marks the surfaces of the disks with markers indicating the start of a recording block (typically today called sector markers) and other information like block CRC to be used later, in normal operations, by the disk controller to read or write data. This is intended to be the permanent foundation of the disk, and is often completed at the factory..."
"User instigated low-level formatting (LLF) of hard disk drives was common for minicomputer and personal computer systems until the 1990s. IBM and other mainframe system vendors typically supplied their hard disk drives (or media in the case of removable media HDDs) with a low-level format. Typically this involved subdividing each track on the disk into one or more blocks which would contain the user data and associated control information. Different computers used different block sizes and IBM notably used variable block sizes but the popularity of the IBM PC caused the industry to adopt a standard of 512 user data bytes per block by the middle 1980s.
Depending upon the system, low-level formatting was generally done by an operating system utility. IBM compatible PCs used the BIOS, which is invoked using the MS-DOS debug program, to transfer control to a routine hidden at different addresses in different BIOSes"
"Today, an end-user, in most cases, should never perform a low-level formatting of an IDE or ATA hard drive, and in fact it is often not possible to do so on modern hard drives because the formatting is done on a servowriter before the disk is assembled into a drive in the factory."
"Some modern formatters wipe hard disks with a value of 0x00 instead, sometimes also called zero-filling, whereas a value of 0xFF is used on flash disks to reduce wear. The latter value is typically also the default value used on ROM disks (which cannot be reformatted). Some advanced formatting tools allow configuring the fill value.[nb 7]
One popular method for performing only the zero-fill operation on a hard disk is by writing zero-value bytes to the drive using the Unix dd utility with the /dev/zero stream as the input file and the drive itself (or a specific partition) as the output file. This command may take many hours to complete, and can erase all files and file systems.
Another method for SCSI disks may be to use the sg_format command to issue a low-level SCSI Format Unit Command.
Zero-filling a drive is not necessarily a secure method of erasing sensitive data[not in citation given], or of preparing a drive for use with an encrypted filesystem.