SQL Performance - One counter to rule them all - identify CPU/MEM/DISK/NET pressure
No. Say you have a server with:


High PAGEIOLATCH waits
High IO stall times
Low Page Life Expectancy (say, consistently under 30)
128GB RAM


You could fix this scenario with:


Index tuning - because maybe the queries are scanning a table too large to fit in memory
Query tuning - because maybe they're using non-sargable predicates, or not caching
Configuration - because maybe some wacko set max server memory too low, or we're using the wrong Cardinality Estimator for our code
Adding memory - but now you have to check version &amp; edition, because your Windows or SQL Server may not support more memory
Faster storage - but this is one heck of an expensive fix


There's no one metric that tells you which of those solutions is the right one. Welcome to performance tuning. Ain't no easy button here.