I am looking to remove and attach a number of shelfs with containing aggregates from a 2020 onto a 2040. The 2020 is running DOT 7.3 and I am thinking about downgrading the new 2040 to the same 7.3 for the duration of the work. I do not need to worry about the internal disks as they do not form an aggregate with disks from the shelfs + all data has been migrated to shelf based aggregates. I am looking for some documentation on this procedure or some advice from the communities to assist in my planning.
There is no special procedure. Switch off 2020, unplug shelves, connect to 2040, assign disk ownership. If you have data that you want to preserve and move to 2040, it is better to assign disk ownership from maintenance mode to avoid partial aggregate errors. Otherwise destroy aggregates, zero spares and unassign disks on 2020 before unplugging.
How does the system recognise the aggrs / vols from the existing trays? - Is it a good idea to downgrade the new system to the same DOT version for the duration of the work, then upgrade once all is working well?
aggregate/volume configuration is kept on disks. System will pick them up by scanning new disks. Make sure to rename volumes and aggregates before moving to avoid conflicts with existing ones on target system.
If target system has new DOT version, there is no need to downrade.