After a successful migration from RHEL5 to RHEL6 (both 64bit) of zimbra 7.2.1. I went ahead and tried to upgrade ZCS to version 8.0.
During the upgrade someone else connected to the server and ran "service zimbra restart" - this interfered with the upgrade and made it fail with this error:

Sun Oct 7 08:18:55 2012 Schema upgrade required from version 90 to 91.
Sun Oct 7 08:18:55 2012 Running /opt/zimbra/libexec/scripts/migrate20120410-BlobLocator.pl
Sun Oct 7 08:18:57 2012 Sun Oct 7 08:18:57 2012: Verified schema version 90.
Sun Oct 7 08:19:18 2012 ERROR 1054 (42S22) at line 1: Unknown column 'volume_id' in 'mail_item'
Sun Oct 7 08:19:18 2012 Sun Oct 7 08:19:18 2012: Error while running '/opt/zimbra/bin/mysql --user=zimbra --password=QUlKJ8JX7.FsAZXaUTzQqiaw --database=zimbra --batch --skip-column-names'.
Sun Oct 7 08:19:18 2012 Script failed with code 256: - exiting
Sun Oct 7 08:19:18 2012 UPGRADE FAILED - exiting.
Now I'm running ZCS version 7.2.1. on RHEL6 with the /opt/zimbra/store folder that was in use during the failed upgrade procedure. Zimbra server works fine with this "store" folder, but there's no chance to successfully upgrade to version 8. Errors I get are the following:

Sun Oct 7 10:25:27 2012 Checking ldap status...
Sun Oct 7 10:25:27 2012 *** Running as zimbra user: /opt/zimbra/bin/ldap status
Sun Oct 7 10:25:27 2012 not running.
Sun Oct 7 10:25:27 2012 Starting ldap...
Sun Oct 7 10:25:27 2012 *** Running as zimbra user: /opt/zimbra/bin/ldap start
Failed to start slapd. Attempting debug start to determine error.
50713c9c lt_dlopenext failed: (back_hdb.la) file not found
50713c9c config error processing cn=module{0},cn=config: <olcModuleLoad> handler exited with 1

Sun Oct 7 10:26:04 2012 failed with exit code: 256.
Sun Oct 7 10:27:40 2012 UPGRADE FAILED - exiting.
I don't know if the two are related - something happened during mysql upgrade, now I get errors when starting ldap during upgrade procedure. I don't know where to begin solving this issue. The command "sh -X /opt/zimbra/bin/ldap start" gives me the same error (tried running this command after the failed upgrade).

BR,
Damien