The old server had 8 processors and the new server has 16, but remember that our new server is a 64bit machine and the old one was 32bit.
The main difference between 32 and 64 is the amount of memory that can be addressed.
The max server memory in the new server is 2147483647 MB and in the old one it was 7000 MB
I would suggest that you configure the max memory on the new one to be the same as the old. With 64 bit, the memory needs to be limited. You can try setting the max degree of parallelism to 4 or 8. I doubt it will make that much of a difference. Not 6 hours of difference.
Are the drives direct attached? SAN? Are they RAID arrays or single drives?
Are all queries running slower or just one or two?
The one that's gone from 30 min to 7 hours, is it a single query or a complex procedure. If the latter can you run it piece by piece to find where the worst performing portion.
How did you migrate the DB? Backup/restore, detach/attach?
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: Discussions on DB performance with occasional diversions into recoverability
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