We’ve tested it several times but always with a fresh copy of the old dataset. After a couple of weeks and as soon we we’re sure that we’ve reverted the changes of the previous owner successfully, we’ve run the upgrade and migration once.
That’s definitely worth a try but I’m not quite sure how long this will take. But yes, we should consider a full vacuum. Especially as we had some problems with the older database already.
Yep. All of the data is stored onto a server ssd and backed by 40GB RAM (of which ~60% are used overall without plateaus at 100% on higher loads).