Cannot copy files to RN316 although I have 22TB free...

Your posts were caught by the automatic spam filter - I released this one.  Not sure if the others had the same information, or if there was additional stuff.  If the latter, let me know, and I can release the others.

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Platypus69 wrote:

Not sure with what's going on with md127 versus md126, whatever they are? Mount points?

 

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Your volume has two RAID groups - the original RAID-5 group, and the second RAID-5 group that was created when you vertically expanded the array to 6x10TB.

The main RAID group is md127, the second group is md126.  These are concatenated together to give you a single volume.

Not sure what is confusing you about the numbers above, they look like they are consistent with your overall used/free information.  One thing that is confusing is that you say you upgraded 8 TB ironwolf drives to 10 TB.  The sizes of md126 and md127 look you like might have upgraded 4 TB ironwolf drives to 10 TB.

Have you looked for errors in system.log and kernel.log?

As an aside - though you do have plenty of free space, you might want to reconsider use of the "smart" snapshots.  The problem with them is that the oldest are retained forever.  Setting up custom snapshots with fixed retention is IMO a much better approach.  Something to consider when you resolve your problem here.