Here is an interesting article on hard drive reliability. Now that there are customers, such as Google, with hundreds of thousands of hard drives in service, there is becoming a database of actually performance characteristics. What I found most interesting is that the type of drive is not particularly important. I had always assumed that the extra money I paid for SCSI drives would be rewarded by longer service life. The findings seem to indicate that environmental factors, such as heat and power fluctuations, kill drives no mater what technology is being used. I'll spend more money on the environment and less on the disks.