Monitoring and Tuning Your Server
Monitoring and Tuning Your Server |
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To determine the extent to which the performance of the File System Cache correlates with the size of the cache, compare the size of the cache over time to the rate at which data sought in the cache is found there. Use the Memory\ Cache Bytes counter as an indicator of the size of the cache. Use Memory\ Cache Faults/sec as an indicator of the rate of cache misses, and Cache\ MDL Read Hits % as an indicator of the rate of cache hits.
If Memory\ Cache Faults/sec increases and Cache\ MDL Read Hits % decreases when the system has reduced the size of the File System Cache, the cache might be too small to really benefit the server. A less effective File System Cache is likely to degrade the performance of an IIS 5.0 server significantly, especially if the size of the cache is often reduced because of a general memory shortage.
If cache performance is poor when the cache is small, use the data you have collected to infer why the system reduced the cache size. Note the available memory on the server, and the processes and services running on the server, including the number of simultaneous connections being supported.
When you add physical memory to your server, the system allocates more space to the File System Cache. A larger cache is almost always more efficient, but typically it’s a case of diminishing returns—each additional megabyte of memory adds less efficiency than the previous one. You must decide where the trade-off point is: the point at which adding more memory gets you so little improvement in performance that it ceases to be worthwhile.
In addition, defragmenting your disks makes it more likely for related pages to be copied into the cache together. This, in turn, improves the hit rate of the cache. Finally, consider reducing the workload on the server by moving some of the load to another server. For more information, see Administering an ISP Installation in this book.