I currently have a few Dual Core Dual Xeon servers and some regular Dual Xeon servers running Windows 2003, and i am facing some performance issues that i can't quite explain at this point.
For the sake of this post, i will just refer to one server of each type, although this issue is happening with many different servers. All servers are running IIS 6.
The dual core servers have 4 SATA drives in a raid 5 and have 3GB of memory. The regular dual xeon servers have 14 smaller SCSI drives in a raid 5, and 4GB of memory. CPU speeds are 3.0GHz with HT for dual cores, and 2.4GHz with HT for single cores.
The problem that i'm facing is that IIS wise, the single core servers are completely outperforming the dual cores. The dual core servers have around 1500 web sites hosted, and can take no more. The single core has 1700 right now, and is showing no signs of slowing down and i can easily add more sites.
Obviously, part of this is likely the performance gain of the SCSI drives over the SATA ones, however i do not believe that this issue is related to disk throughput.
On the dual core servers, if i go to add a new application pool, restart IIS, or basically do anything with IIS, it will just hang. The usual solution is to restart IIS (have to force it to kill all of the worker processes). Initially i thought this problem was due to IIS's metabase simply being too large, however the single core boxes seem to have no problem with this.
At this point, i am beginning to entertain the fact that this is a hardware problem with either the motherboard or the raid controller, however motherboard is supermicro x7dva and raid controller is a 3ware 9000 series, which i am having a hard time believing are the cause of hte problems. I currently have many servers with the same configuration running FreeBSD and they are having no problems whatsoever. All drivers are the latest version.
If you have bothered to read this far through this long post, thank you for your interest. I am looking for any and all suggestion and comments, no matter how simple or complex they might be.
You might need to do some performance monitoring on Win2k3 (Administrative Tools -> Performance) to work out what's the bottle neck.
Also you might wish to turn off HT from the BIOS. From my experience they severely slow down applications (especially SQL Server in my case) as the HT pipeline does not handle certain op-codes, and processes binded to HT can become very slow.