I am building a server which will host various websites on IIS, and also have multiple MSSQL databases. I'm currently trying to decide between 2 x AMD Opteron 6128's (8 cores each) and 2 x Xeon E5620's (4 cores each + Hyperthreading).
What do you think would be the better choice, and why? I can't find too many benchmarks of those two in a web application scenario like mine. Thanks for your help!
Given equivalent base core performance a processor with X physical cores will outperform a processor with X/2 cores + HT. Generally. There are some workloads that don't live well on HT, among them are disk I/O threads and small-data pure compute threads (think rendering). And others that just don't care, such as IIS. MS-SQL has a history of not working well with Hyperthreading when heavily loaded.
In the end, figuring out whether or not HT will help you will require running your apps on it and seeing for your self. There is just too much variety in the constellation of IIS/MSSQL web applications to make any broadly applicable generalizations.
What do you think would be the better choice, and why?
The one with more discs. Seriously.
Put in enough memory and your websites will have to be very special do even start using the processor. I remember serving 400.000 visitors per hour on a dating site I made for a customer during a peak (tv appearance) with a dual pentium.
BUT: multiple sql server databases will use a lot of IO. This is a LOT more important than focusing on CPU because it is a lot more likely bottleneck. So, take the one where you can put in 10 or 12 or more drives and that is going to give you a lot better SQL performance. With fast discs.
