@GeoffA Thanks for the excellent response here.
Absolutely. We run the same import code in Rockstor 3 (fully updated) as in Rockstor 4. But with ongoing bug fixes and improvements. Any Rockstor 3 created pool should import without issue, given it’s in good health, into Rockstor 4. In fact given the far newer btrfs in Rockstor 4 we have had a few reports of 4 importing where 3 failed. But that was mainly down to poorly pools that needed the newer, more capable underlying software from upstream. We unfortunately failed somewhat in maintaining a sufficiently new enough kernel backport arrangement in our CentOS offering that we are no longer required to maintain now that we have re-based on openSUSE who officially support btrfs, at least for the default system drive install arrangement.
But note that if the pool is large it may take a while to import. Especially the quota info. So be patient. This also depends on the capabilities/speed of the hardware of course.
Hope that helps.
As an additional note of caution. I like to recommend the use of a new installer disk for the new install as then you avoid having to wipe the previously system disk. Also, to avoid accidedntally selecting a data disk, it seems prudent to disconnect them entirely. Do the new install and all it’s updates etc. Then power cycle to ensure all boots up ok, then power down, reconnect all data drives, then power up and do the import.
But as @GeoffA states, do nothing until you have 1 or ideally 2 known good backups as all non trivial software is buggy and a typical OS has a tone of non-trivial software.