Have taken a copy of the production database (14G) and successfully migrated it to the 1.8 schema.

On migrating it to the 2.0 schema, the script reaches this section of SQL in upgrade.sql

SELECT e1.eventid,(SELECT e2.value
FROM events e2
WHERE e2.source=e1.source
AND e2.object=e1.object
AND e2.objectid=e1.objectid
AND (e2.clock<e1.clock OR (e2.clock=e1.clock AND e2.eventid<e1.eventid))
AND e2.value<2
ORDER BY e2.source DESC,
e2.object DESC,
e2.objectid DESC,
e2.clock DESC,
e2.eventid DESC,
e2.value DESC
LIMIT 1) AS prev_value
FROM events e1
WHERE e1.source=0
AND e1.object=0
AND e1.value=0
HAVING prev_value IS NULL OR prev_value = 1

At that point the process takes an eternity to run. I have let it run for 5 days and abandoned it. I have heard of others (see the Forum) running this bit of SQL for 11days.

This length of database migration is not practical for a production environment. See my comments in the users forum. (http://www.zabbix.com/forum/showthread.php?t=27486)

I see three potential resolutions:-

(1) Revise the code so it runs in a realistic time on sensible hardware.
(2) Have a two stage migration where the core configuration of Hosts/Host Groups/Users/Templates etc etc are migrated fairly rapidly and then a second stage where the history is migrated and re-integrated into the database.
(3) Could be a by product of (2) - accept that it is not practical to migrate history and abandon that data and limit the migration to Hosts/Host Groups/Users/Templates etc etc