Let me start off with a short question on which I will elaborate below: What setup would you use for a home file server that is highly unlikely to lose data, but keeps the cost down as much as possible?
I am currently looking to upgrade the home server (details of the current setup are below). I'm looking for something that mainly can act as a NAS, but if it's not too much more expensive it would be nice if it could also host a Plex server, a VPN server and maybe some other small things. It will store documents, photos, music and videos, in total approximately 3Tb. My main concern is data integrety and secondly speed and availability. E.g. I wouldn't mind a week of downtime when a drive fails.
It seems it is recommended to have three copies of all the data of which one is off-site. In my case, the second copy would be on a server at my parents place, sychronized via the internet. The third copy I would create on a local external hard drive that is only connected during the backup.
The problem now is: how do I guarantee that the data is consistent across all drives and that no files have been changed? Locally this could be done using ZFS and its checksumming, but this requires several drives at a single location dramatically increasing the cost of the setup.
Another problem is how to handle versioning of the data. E.g., in case of emergency I would like to be able to access last months data. Also this points seems nicely covered by ZFS, but again only seems like a viable option with more drives.
Currently I'm using two Raspberry Pi 2's as a file server, each with one external hard drive attached. Both are in different location, host their own files and backup to the other over the internet using rsync. Versioning is done using hard links. At the time I put this together I figured that in the event that one of the servers went down I could simply take the other offline, buy a new Pi and HDD and copy the good drive to the new server. However, both drives are formatted with ext3 and I have recently come to the understanding that errors in the stored data might not immediately be noticed. This did alarm me as the whole point is to keep the data safe. Hence this question.
Also, at the time I did not take into account that during the recovery the only good disk would be stressed a lot, of course making it more likely to break having me lose all of my data. Using this reasoning I keep adding redundant drives everywhere, of course increasing the price a lot. This bring me back to the original question: at what point do you have enough redundancy in a home storage solution?
--checksumoption. Having the cloud backup at the offsite / cloud at your parents, and having the local backup to the external would seem like enough to me. Use the tools you are already using to verify data integrity, etc. You should be able to usefsckto check the status of theext3formatted partitions. It sounds like you're only interested in retaining a 100% accurate and non-corrupt copy of the data in the event of a disaster, etc. and performance and availability is not of such a concern, I'd try to test and use something like that.