I really need your input on recovering my failed upgrade to 4.2.
First two things to do to get appropriate help would be, in my opinion:
1) provide a detailed description of your environment
exact version before the update; kind of storage (Gluster, NFS, iSCSI, FC), kind of hosts (plain OS and which version or node-ng and which version before and after), kind of deploy executed for hosted engine VM at initial install time (appliance, full OS).
Describe steps used for upgrading.
2) upload to a shared file services all the possible logs:
engine logs before and after the upgrade and logs of engine-setup run during update