I have recently upgraded my 1.5 TB 2005 database to 2012. I have a larger machine with faster disks, more processors and 3 times the amount of memory. My users select statements are running faster, but inserts are reportedly slower. I tested one insert which does a half-nasty subselect...it runs in 20 minutes on 2005 and ran for 9.5 hours on 2012 before I eventually killed it.
I have elimanated a disk IO issue by running a load test on just the disk.
Any ideas? I can provide any information you need.
Thanks in advance!