Backup company Backblaze has put out another juicy status report on the reliability of its massive collection of hard drives <https://blocksandfiles.com/2022/11/01/backblaze-disk-drives/>. This one has some interesting numbers on the cost of dealing with drive failures -- it seems the hardware cost of these to the company is zero, as the failed drives get sent back to the vendors for full credit or replacement. (I guess if you buy a few thousand units at a time, you get special deals like this.) Since the company is in the business of providing sufficient redundancy that the impact of a drive failure on data integrity is essentially zero, the main cost of a failure becomes the labour cost of putting in a new drive, which comes to $300. Looked at this way, looking at the table which compares three models of drive, with unit costs ranging from $225 up to $275, and corresponding annualized failure rates of 1.5% down to 0.5%, it turns out the cheaper, flakier drive is the better deal -- amortized over a five-year service lifetime, the increased labour cost of replacing failed drives is easily outweighed by the savings in buying the drives in the first place.