High-end "enterprise" drives versus "consumer" drives?
Interestingly, we observe little difference in replacement rates between SCSI, FC and SATA drives, potentially an indication that disk-independent factors, such as operating conditions, affect replacement rates more than component specific factors."
Maybe consumer stuff gets kicked around more. Who knows?
Infant mortality?
. . . failure rate is not constant with age, and that, rather than a significant infant mortality effect, we see a significant early onset of wear-out degradation.
Dr. Schroeder didn't see infant mortality - neither did Google - and she also found that drives just wear out steadily.
Vendor MTBF reliability?
While the datasheet AFRs are between 0.58% and 0.88%, the observed ARRs range from 0.5% to as high as 13.5%. That is, the observed ARRs by dataset and type, are by up to a factor of 15 higher than datasheet AFRs. Most commonly, the observed ARR values are in the 3%range.
Actual MTBFs?
The weighted average ARR was 3.4 times larger than 0.88%, corresponding to a datasheet MTTF of 1,000,000 hours."
In other words, that 1 million hour MTBF is really about 300,000 hours - about what consumer drives are spec'd at.
Drive reliability after burn-in?
Contrary to common and proposed models, hard drive replacement rates do not enter steady state after the first year of operation. Instead replacement rates seem to steadily increase over time.