[Lramseyer]

I am not sure what the other comments are going on about, but let me give you a little bit of my perspective, since I have a few years of experience in the HDD industry.

An all zeroes pattern would look nothing like all zeroes on the media. Modern read/write channels use a scrambler, RLL, and LDPC, which scrambles the data, limits the length of long magnets (since the heads don't like DC signals,) and then parity bits. From a signal processing perspective, writing random data will not look much different from all zeros.

One thing to keep in mind, however; if you tell the drive to write a large range of LBAs to the same pattern, depending on the firmware, it might only write one physical sector and point every LBA in that range to that physical sector. So now your data only has the first sector overwritten. If someone hacks the firmware in a way that allows reading of physical sectors, they can get your data.