We had a hardware failure on one DB Server, and had to restore SQL 2000 DBs to a DB Server with SQL 2005. We changed Compatibility Mode to 80. Users are functioning, but are reporting slowness and time-outs. The machine we restored to has a faster processor and double the RAM. Neither are experiencing average utilization above 50%. In fact, we see no hardware issues in any of the machines involved in the path from Web Server to App Server to DB Server to SAN. Users on other DB Servers are not experiencing problems, but none of those have utilized backwards compatibility.
Are there any known significant performance issues relating to utilizing backwards compatibility???? And/Or, any suggestions on where to look further to isolate the true problem, and to fix it?