RN516 Expansion to 24TB?

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herbg wrote:

Now, with a larger volume, I plan to re-enable Snapshots again.

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FWIW, I always recommend against using the smart snapshots.  The problem with them is that the oldest snapshots are retained indefinitely, so eventually you will need to manually delete them for each share (or run out of space).

Instead, I suggest using Custom snapshots.  Here are the settings I use for most shares:

You can of course adjust the retention setting as desired - to balance the snapshot space against the benefit of keeping the older versions.

BTW, if you check "Allow Snapshot Access", for some reason the NAS will allow you to write to the snapshots.  Personally I think that's a horrible decision on Netgear's part, since for me the most important reason for snapshots is to ensure I have a copy of older versions.  So I also recommend against checking that box.

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herbg wrote:

For maintenance, is Scrubbing, Disk Defragmentation, and Balancing advisable?  I have never used these utilities but the Knowledge Article is a bit confusing when bit-rot protection is enabled.  Since this backup NAS has been in used for 9+ years, I thought it was time to do some maintenance! 

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I don't think that the setting for bit-rot protection should affect your maintenance schedule.

I run each of the maintenance functions (include the disk test) once every three months (spread out over the quarter).    I don't see any need to run them more frequently myself.  

Scrubbing (and/or the disk test) can give you early warning when the disks begin to fail, since both tests require accessing every sector of every disk.  

With BTRFS, there is a distinction between free space and unallocated space.  The file system needs a reasonable amount of unallocated space to run properly.  Periodically balancing will reclaim unallocated space (from the allocated free space).  The frequency needed for balances depends a lot on your usage.  If it takes a long time, you aren't doing it often enough.  It usually completes in 15 minutes or less on my systems.  

Defrag is the hardest one to figure.  Too much fragmentation can hurt performance, but defragging also tends to increase the space needed for snapshots.  Many people choose not to run it at all.  If I were going to drop one maintenance function, it'd be defrag.