P[drive failure]: How reliable is your NAS?
![P[drive failure]: How reliable is your NAS?](https://wsrv.nl/?url=khz.ac%2Flow-voltage%2Fdrive-failure%2Fbackblaze-drive-failure.png&w=360&h=480&fit=inside&we=&output=webp&q=80)
A personal blog post details the author's plan to build a reliable NAS for lifelong data storage, using four 8TB drives in a two-site btrfs RAID1 setup. The author analyzes failure modes—whole-drive failure and latent sector errors—and uses recent Backblaze data to estimate failure rates, concluding that even with redundancy, the probability of losing data over 50 years is non-trivial, and that drive failure rates are roughly constant over time, contrary to the classic bathtub curve.
Nothing is forever. P[the world ends tomorrow] > 0, after all.
- zootboy
To be honest, it seems rather silly to go this deep into probability calculations when your N = 4 (hard drives). I can present numerous wildly-differing anecdotes about how single hard drives I have owned have fared. I have some drives that are 20 years old that still apparently work fine. I've had brand new drives silently corrupt sectors after less than a year in use. Trying to put hard numbers to the probability of failures is a fool's errand. Better to simply assume that components will fail over time, and architect your system to handle those failures gracefully.
That said, I actually agree with much of the final architecture decisions made by the author. BTRFS raid1 with an offsite copy in a geographically distant area is a pretty good solution for the average person's personal documents. Possible improvements would be:
- Multiple offsite copies in different locations
- Hardware diversity (differing models of HDD, host PC, power supplies, etc.)
- Staggered hardware upgrades on a 5-10 year cycle
- Cold storage (offline) copy
- wao0uuno
What a long and convoluted way to arrive at the most obvious conclusion. Use redundant storage (mirrors) for important data and have backups (3-2-1 rule).
Don’t waste money on redundancy if your data can be easily reacquired.
- ares623
off topic but I really like the design of the site