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from the confidentiality-integrity-and-availability dept.
Exotic Silicon has a detailed exploration of how and why to make long term backups.
The myth...
When thinking about data backup, many people have tended to fixate on the possibility of a crashed hard disk, and in modern times, a totally dead SSD. It's been the classic disaster scenario for decades, assuming that your office doesn't burn down overnight. You sit down in front of your desktop in the morning, and it won't boot. As you reach in to fiddle with SATA cables and clean connections, you realise that the disk isn't even spinning up.
Maybe you knew enough to try a couple of short, sharp, ninety degree twists in the plane of the platters, in case it was caused by stiction. But sooner or later, reality dawns, and it becomes clear that the disk will never spin again. It, along with your data, is gone forever. So a couple of full back-ups at regular intervals should suffice, right?
Except that isn't how it usually happens - most likely you'll be calling on your backups for some other reason.
The reality...
Aside from the fact that when modern SSDs fail they often remain readable, I.E. they become read-only, your data is much more likely to be at risk from silent corruption over time or overwritten due to operator error.
Silent corruption can happen for reasons ranging from bad SATA cables and buggy SSD firmware, to malware and more. Operator error might go genuinely un-noticed, or be covered up.
Both of these scenarios can be protected against with an adequate backup strategy, but the simple approach of a regular, full backup, (which also often goes untested), in many cases just won't suffice.
Aspects like the time interval between backups, how many copies to have and how long to keep them, speed of recovery, and the confidentiality and integrity of said backups are all addressed. Also covered are silent corruption, archiving unchanging data, examples of comprehensive backup plans, and how to correctly store, label, and handle the backup storage media.
Not all storage media have long life spans.
(Score: 2, Interesting) by shrewdsheep on Tuesday February 06 2024, @11:44AM
I second this skepticism of RAID1 solutions. I ran a RAID for a couple of years. The main disadvantages I perceived was the power consumption (both drives constantly on), the required monitoring plus the lack of protection against anything but hardware failures. I never had to recover a full drive but anecdotally, I hear that people ran into errors for the problem of silent corruption that you mention.
Instead I have settled for an "rsync-RAID" once a day including backup of modified/deleted files. This solutions therefore includes protection against user error as well (once in a while these backups have to be cleared out to retain capacity, though). Additionally, the backup drive is powered down and unmounted for 95% of the time, hopefully extending its life time expectancy and thereby de-correlating failure times of the two drives. I switch drives ever ~5 yrs and I have yet to experience a drive failure.