Backup solution: hash/checksumming and/or error correction

Question

I'm trying to keep my data well protected with backups, using multiple hard drives (basically swapping the backup disk out every week). For checking validity, I was originally planning on md5summing or perhaps only crc32 summing the content and verifying them periodically. I realize also that tools such as par2 exist that make error-correction files at the cost of extra disk space.

My question is if there is any reason to waste the processing time and disk space on error-correcting parity tools (which seem to be designed for usenet or optical storage) or if 2 or 3 copies of the files (one in use, two backups) plus simple hashing/checksumming for validity are enough?

Answer 1

Let me put it this way: I have been backing things up for about 23 years now, and never once have I had to worry about file corruption, nor have I ever had any that I knew of.

Modern backup software can do a verify as part of the backup job, and to me, that seems sufficient. I always recommend multiple copies of a backup in case the entire backup is faulty, and that you test them periodically to make sure you can restore.

Balance this advice against just how valuable the data is, but what you want to do seems like overkill, and a lot of extra work to me.