Clustra/HADB did use disks (can't have all your data disappear if you turn off the cluster!) but a running system was in-mem in operation -- if your database wa

Clustra/HADB did use disks (can't have all your data disappear if you turn off the cluster!) but a running system was in-mem in operation -- if your database was much bigger than the RAM available it was unusable. (I never used Hypra.)