Useful PerfMon counter KPIs in Web Performance testing

Object\Counter	Preferred or Ideal Value
Memory\Pages/sec	0–20. (Unhealthy if greater than 80; probably indicates not enough RAM.)
Memory\Available Bytes	10% of physical memory.
Memory\Committed Bytes	No more than 75 percent of physical memory.
Memory\Pool Nonpaged Bytes	A steady value. (A slow rise might indicate a memory leak.)
Processor\% Processor Time	Less than 75 percent.
Processor\Interrupts/sec	Depends on the processor, and on network hardware and drivers. Up to 3,500 for a 90–megahertz (MHz) Pentium; more than 19,000 for a 500–MHz Pentium or more than 58,000 for a 1.5–gigahertz (GHz) Pentium. Lower is better. If the value is too high, try moving some hardware devices to a different server.
Processor\System Processor Queue Length	4 or less.
LogicalDisk\% Disk Time PhysicalDisk\% Disk Time	As low as possible.
LogicalDisk\Avg. Disk Queue Length PhysicalDisk\Avg. Disk Queue Length	Less than 4.
LogicalDisk\Avg. Disk Bytes/Transfer PhysicalDisk\Avg. Disk Bytes/Transfer	As high as possible.
System\Context Switches/sec	Compare this value with the value of Web Service\Total Method Requests/sec. Context switches per request (Context Switches/sec divided by Total Method Requests/sec) should be low.
System\System Calls/sec	As low as possible.
Web Service\Bytes Total/sec	As high as possible.
Web Service\Total Method Requests/sec	As high as possible.
Web Service\Current Connections	As high as possible.
Web Service Cache\File Cache Hits %	As high as possible for static content. Note: This value might be low if the Kernel URI cache hits percentage is high.
Web Service Cache\Kernel:URI Cache Flushes	As low as possible, relative to the number of requests. Note: This number increases every time a file is flushed from the HTTP.sys response cache (HTTP.sys is the kernel-mode device driver in IIS 6.0), which means that the content has not been accessed in the past 2–4 minutes. The only way to decrease this number is to flush the cache less often, although frequent flushing can cause HTTP.sys to use more memory for content that is not being accessed.
Web Service Cache\Kernel:URI Cache Misses	As low as possible. (Each request for dynamic content increases the value of the counter by one.)
Web Service Cache\Kernel:URI Cache Hits %	As high as possible. (Applies to static unauthenticated content and dynamic content that is marked as cacheable.)
Active Server Pages\Request Wait Time	As low as possible.
Active Server Pages\Requests Queued	As low as possible.
Active Server Pages\Transactions/sec	As high as possible. Note: ASP transactions degrade overall server performance because each transaction requires interaction with a database. If you are concerned about server performance, use ASP transactions sparingly.