[mubley]

Originally Posted by KevinH

Seems you've got a dup path in the volume table. Can you login to MySQL manually and dump that table. Might have to remove a path to get the update to run.

Here's the detail of how to implement KevinH's suggested workaround:

NOTE: If you have already attempted to upgrade to 3.1, you will need to revert to a backup of your M2 installation before continuing.

First, switch to the zimbra account:

su - zimbra

Next, launch the mysql client utility:

mysql

Tell mysql that you want to work on the zimbra database:

connect zimbra;

Drop the index called i_name:

alter table volume
drop index i_name;

Drop the index called i_path:

alter table volume
drop index i_path;

Quit the mysql client utility:

quit

Finally, switch back to the root account:

exit

You should now be able to successfully upgrade from M2 to 3.1.