I make my decision based on drive failure rates from Backblaze. They are a respected online backup company running banks of external hard drives with a total count of over 300,000 external drives. I wanted the best balance between size and MTBF (mean time before failure), or Backblaze’s new preferred standard, AFR (annual failure rate). Bigger drives fail more often than smaller drives.
Based on Backblaze’s hard drive failure numbers five years ago (the last time I bought a set of three external backup drives), I decided 4TB drives were the ideal size given the “size vs failure rate” data at the time. Seagate is my preferred brand. Things have changed. Larger size drives are doing better statistically now than they were 5 years ago. Based on the most recent Backblaze numbers (chart above and link below), I decided to get a total of three 8TB Seagate external hard drives this year. With larger drives doing better than in the past, Backblaze is slowly retiring their 4TB drives.
Why three backup external hard drives? Read the 3-2-1 Photo and Data Backup Plan. Do NOT trust your precious files and photos to just one external drive.
Long ago, and before I knew about Backblaze’s data, I had periodic drive failures using other very well know hard drive brands which I will not mention. I switched to Seagate due to Backblaze data.
As added protection I use battery backups with surge protection so my computers keep working if the power goes off (long enough to shut them down properly), and they are protected from voltage spikes.
Despite battery backup and surge protection, I lost one external hard drive a dozen or so years ago due to a power outage. Even if you try to do everything right, something can still go wrong.
Links:
More information from Backblaze
The 3-2-1 Photo and Data Backup Plan
Memory Cards Part 1: The Best Way To Use Memory Cards To Avoid Lost Images
Memory Cards Part 2: Lost Photos
My Hard Drive Crashed (Burned, Drowned)! Where Do I Send It To Get My Data Back?
The Best Online Backup For Your Photos and Other Important Files
Backblaze – first rate cloud storage
DriveSavers – If you need someone to recover the data from your hard drive, this is the company to go to.