Physical Hard-Disk Data Arrangements and Drive Failures?

Tadau asks: "Knowing not much of the low-level and molecular aspects of a hard drive platter, I'm wondering if it is possible to cause a weight change/imbalance on a hard drive platter by say writing solid 1's to approximately 1/2 of a side of the platter? If there is a weight change, then could that attribute to drive vibrations by an ever-so-slightly unbalanced platter, which may result in an eventual drive failure?"

Comments

I worked in the HDA industry

[nytes]

The answer is yes. If you write all 1's to one side of a drive, and all 0's to the other side, the drive will eventually fail.

Simple answer

[missing000]

No.


If you could however write all 1's to all the harddrives in the Southern Hemisphere it would likely cause a polarity shift on the earth however. (AF)

Historically you're 100% right

[shoppa]

You are, of course, 100% right historically-speaking. Hard drives and tape drives used to use "NRZ" or "Non-Return-to-Zero" recording, where ones were recorded with a magnetic flux change and a zero without a flux change. The problem was actually much more severe with 7-track 556 BPI tape recordings, where the weight imbalance would cause the tape drive to actually jump up and down on the floor.

Once a year, (traditionally, the first day in April) all disk and tape drives were rebalanced by redistibruting ones and zeroes. The "bit buckets" were also emptied on this hallowed day.

This isn't a problem anymore because all modern recording media use "MFM", "RLL", or "GCR" encoding methods, where ones and zeroes are automatically balanced.

One minor technical nit: "ones" actually weigh less than "zeroes". This led to the conclusion that the more data you put on your punched cards, the less they cost to mail :-)