This, my friends, is a problem.
And here, my friends, arrives the solution:
4 units of 1 terabytes each. After RAID10, that's a nice 2 TB of storage for aprs.fi.
This is just for the backups. I'll need to get 4 more of these within a couple of months to upgrade the live servers.
Thanks go to an anonymous Finnish site user for the donation of 2 disks (and organizing delivery in 26 hours), and all other donors for the other two!