Question about redundancy and RAID on home NAS

1. offizieller Beitrag

    Here is what I want to achieve:

    • have a pooled file system of all drives which:
      • has some redundancy
      • can seamlessly be imported to another system if I change the OS or the machine
    • allow for mobile uploads (using OpenVPN is fine)
    • have a gallery with AI facial recognition which uses the ready folder structure (this seems to be very difficult to find)

    I currently have a HP Microserver N36L which can have 5 SATA drives. Given my current experience I would go with OMV, Nextcloud and Photoprism/Pi2gallery. I have very limited knowledge on the dos and don'ts of redundancy and file systems though, so I would like advice on how to setup the drives in the most practical manner which gives me redundancy and portability as above.


    What setup would you advise? Thanks

    • Offizieller Beitrag

    I notice that you don't mention backups.


    I would recommend that you start with a robust backup system and only then start to consider if you also need some form of redundancy. The backup copy (copies) can be used to import the data to some other OS or server, if needed. Naturally you need to verify that it is possible by actually doing it, before you assume that it is possible.


    You could use some of the drives in the NAS for backups. Or external hard drives. Or another server. Or an extra drive in a PC in the LAN. Or an external drive connected to a PC. Or the cloud. Or various combinations.


    I use several OMV servers and backup one server on another using rsync.


    For pooling drives I use mergerfs. I don't use any redundant filesystem.


    You could use a small rpi4 to backup your NAS. I have a rpi4 with four 16TB drives pooled using mergerfs. Works more than fine enough to use for backups.

    Hi, thanks for the reply. Yes, I am planning on implementing a 3-2-1 but here I would like to clear up this main NAS first.

    Mainly, I wonder whether a software RAID can be recognised by another system (say if the OMV boot drive fails). Also, is a RAID rebuilt too slow and painful?


    Do I understand correctly that if a drive fails in your setup, you just replace it and then rerun rsync from the other backup servers? This sounds like a manual RAID with the added benefit of having separate machines, so it should be more robust. Is it faster or slower than a RAID rebuild?

    • Offizieller Beitrag

    I have no real experience with RAID. Software or hardware. By intention. It seems very complex and difficult. Not to setup. That looks very easy. But what to when something goes wrong seems very difficult.


    Yes, if a drive fail I can replace it and restore what was on it from my rsync backups. Or I can simply immediately start accessing the lost content from one of the backups. If I need to. The time it takes to restore the data depends on how the transfer is done. SATA on the same server is fast. Ethernet is slow. I suspect a RAID rebuild is even slower...


    It can get more complicated using mergerfs pooled drives. Then just some files may be missing from the filesystem. You can then use rsync to just restore the missing files from backups. But you may have to do this several times if the pool was backed up as several separate folder trees or used for several separate shared folders.


    I have never had to restore a whole drive like this. So far. But I have often had to restore a specific file or folder that I deleted or messed up. When I update servers I sometimes pretend the old server is destroyed and create the new server by reinstalling and restoring from backups. If the disk is big, say 12TB or 16TB then it can take a day or so over the network. Sometimes I simply connect the drives together using SATA in another computer and do the copy there. Afterwards I may use the old server as an extra backup of the new, at least for a while.


    All my servers use NFS and autofs. This means that all my servers can access all shares on all the other servers. And I use rsync to create backup snapshots using this.


    If I used to use the path /srv/nfs/nas0/music to access my music library, and nas0 is gone, I can instead use /srv/nfs/nas1/snapshots/nas0/latest/music. And there my music is, as it was when I ran the latest backup.

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