Distributed monitoring: Unhandled exception :Request timed out

The problem with the upgrade from 1.2.8 to 1.5 or 1.6 is how should we proceed ?

  1. We have around 3000 hosts which are being monitoring by this old site alongwith lots of customizations on the monitoring server.
  2. The size of the OMD_ROOT is 140GB. We don’t want to loose performance data. Also, our customers have bookmarks.
  3. In terms of contact groups , roles and users, those should also be synced.
  4. This is just some of the configuration as an example. There will be more.