The Bathtub Curve

The economics of long-term data storage are critically dependent not just upon the Kryder rate, the rate at which the technology improves cost per byte, but also upon the reliability of the media over time. You want to replace media because they are no longer economic, not because they are no longer reliable despite still being economic.

Source

For more than a decade Backblaze has been providing an important public service by publishing data on the reliability of their hard drives, and more recently their SSDs. Below the fold I comment on this month's post from their Drive Stats Team, Are Hard Drives Getting Better? Let’s Revisit the Bathtub Curve.

Wikipedia defines the Bathtub Curve as a common concept in reliability engineering:

The 'bathtub' refers to the shape of a line that curves up at both ends, similar in shape to a bathtub. The bathtub curve has 3 regions:

1. The first region has a decreasing failure rate due to early failures.
2. The middle region is a constant failure rate due to random failures.
3. The last region is an increasing failure rate due to wear-out failures.

Depreciation

Source

More than three years ago, based on Paul Butler's The problem with bitcoin miners, I wrote Generally Accepted Accounting Principles. The TL;DR was that the economic life of Bitcoin mining rigs was estimated at 16 months, as Moore's law in a competitive ASIC market rapidly generated more power-efficient rigs. But the Bitcoin miners' accounts were using 5-year straight-line depreciation for their rigs, which was significantly increasing their nominal profits.

Below the fold I look at the same problem unfolding in the heart of the AI bubble.