Palmerston North Re: It is not just about numbers here
Woahhh you had to go back 2 years ... a backup in good order would have been much more adequate.
1) Your company backed up corrupt data ... that can happen but going 2 years without checking its consistency ... that is bad. But at least you have learnt your "Lesson 2" which makes Lesson1 a moot point.
2) Before doing something very sensitive make sure you have the proper procedure and equipment at hand. Usually in HA things come in twos ... at the very least .. so test things before going commando on the production line.
I would add
3) Old backup may be completely useless when they have not been migrated. I've lived such an example where the servers went from x86 to Sparc and the application from C++ to Java ... good luck with finding a 20 year old server in working condition ... may prove extremely costly when data retentive lawyers kick in.
On that point lucky for you the backups agreed with the current firmware/hardware on the switch.