My ideal solution is to have everything backed up "in the cloud" plus have a backup at home. So far I've got the home backup happening - every machine uses 'attic' to back up onto my NAS. I'm still figuring out what the "in the cloud" side looks like.
One thing you can do is keep copies of important documents elsewhere - like Dropbox, a USB drive in a safe deposit box, etc. It all depends on what technologies you trust and how much you trust them.
For OCR, I can't say I've had much trouble with it. Mayan breaks the PDFs into pages, then feeds each page to tesseract. All of that happens in a worker process and I haven't found that it has a significant impact on the use of Mayan. The OCR section for the document will be incomplete for a while though.
[0] http://mayan.readthedocs.io/en/v2.1.4/topics/backups.html