Backup storage: RAID1 or alternating drive?

Vectorspace

Dabbler
Joined
Oct 18, 2019
Messages
13
I want to build a 4TB home NAS for the sole purpose of being a weekly backup destination for my PC (possibly also make it a media server, but not at first). I'll be using FreeNAS, that's why I'm here.

For storage, 2x4TB HDD's, mirrored in some way for drive failure redundancy (separate drive for FreeNAS itself). But what way should I do it?

The simple solution seems to be RAID1. That way everything is always mirrored.
Alternatively, what about A/B alternating backups, where I back up to Drive A and Drive B on alternating weeks? The advantage I see over RAID1 is I get limited versioning. For example if a backup fails and a file gets corrupted. Or if I delete an important file, and then my backup process deletes it from the NAS backup at the next run before I notice, I have a week to get it from the older backup. The disadvantage is if one drive fails, 50% chance it's the drive with the newer backup.

Do people prefer one over the other? Or does anyone have alternative ideas that I haven't thought of?


Some background if anyone is interested
My existing backup destination NAS a repurposed gaming PC. I set it up as a NAS 6 years ago. 100GB HDD for the OS. Running Ubuntu, with Samba to provide the network shares. 2x2TB in RAID10 for the shared storage (RAID10 rather than RAID1 because at the time I read that RAID10 was better, but I didn't realise it only makes a difference with 4+ drives). Storage is getting tight, hence I want to upgrade storage on both my PC and this fileserver.
For the backup process itself, I use FreeFileSync to synchronise the important folders on my PC to the backup share on the fileserver.
Because the NAS's only purpose is to receive the backups, it does not need to be on except while backing up. So I have a batch file that uses WakeOnLan to turn the NAS on, then calls FreeFileSync to do the backup, then calls PuTTY to send a shutdown command to turn it off again.
The only reason I used Ubuntu & Samba is I didn't realise NAS software was a thing then :)
 

blueether

Patron
Joined
Aug 6, 2018
Messages
259
I wouldn't do the latter (Disk A/B)

I don't know but may work for you:
  • 2x4TB HDD in a 2 way mirror
  • Do backup to FreeNAS
  • Do snapshots (read up on these on ZFS)
FreeNAS likes to run 24/7, this allows it to do scrubs and SMART disk tests and warn you of a failing disk
 
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