I have often wondered why there is such a passion for partitioning drives, especially on Unixy OSes (/usr, /var, et al). This does not seem to be a common theme with Windows installations.

It seems that partitioning greatly increases the likelihood of filling one partition while others have a great deal of free space. Obviously this can be prevented by careful design and planning, but things can change. I've experienced this on machines many times, mostly on ones setup by others, or by the default install settings of the OS in question.

Another argument I've heard is that it simplifies backup. How does it simplify backup? I've also heard that it improves reliability. Again, how?

Almost 100% of the problems I have encountered with disk storage is with physical failure of the disk. Could it be argued that partitioning can potentially accelerate hardware failure, because of the thrashing a disk does when moving or copying data from one partition to another on the same disk?

I'm not trying to rock the boat too much, I would just like to see justification for an age-old admin practice.