Web Proxy Server Service: Current Average Milliseconds/Request. This counter shows the amount of time necessary to complete a client's request. This value varies from proxy server to proxy server. User loads, machine hardware, and available bandwidth all play a part in determining it. You'll simply have to get a feel for what is average for your installation and take action if the value rises sharply. Note that momentary spikes in this value are common. As users enter an erroneous URL or a URL that no longer exists, this value is artificially inflated as the DNS request times out or the URL times out. The counter averages this longer time period with the successful requests, creating a spike in the results.
Windows NT 4.0/IIS Performance-Related Counters
If you suspect a performance-related problem with your proxy server, you can do more than look at only the Proxy Server-specific Performance Monitor counters. A host of other counters exist to help you look for bottlenecks. Many publications describe in detail the process for running down general bottlenecks. You can also run a search on the Windows 2000 Magazine Web site (http://www.win2000mag.com/) and find articles such as John Saville, "Troubleshooting NT Performance Monitoring," April 1998.
Memory: Pages/sec. Any value on this counter up to 20 is acceptable. Twenty to 60 isn't good, and anything over 60 means trouble.
Processor: % Processor time. Microsoft says the maximum acceptable value is 75 percent in most cases. A consistent 85 to 90 percent is evidence that the machine is properly scaled and matched to its intended function. A process running consistently near 100 percent means trouble.
LogicalDisk: Queue Length and PhysicalDisk: Queue Length. Both counters should show values less than 2, on average. If you have results greater than 2, suspect the disk or the controller card: The disk or card might have a problem or require an upgrade. Moving from 7200rpm to 10,000rpm disks makes a big difference in proxy server return times.
Process: % Processor Time (Instances: inetinfo, wspsrv) and Process: Virtual Bytes (Instances: inetinfo, wspsrv). I like to monitor these two instances of processor time to understand what resources these two processes are consuming. If a proxy server is about to fail, you can use Performance Monitor's charting function here first to notice a trend.
You'll develop a similar list of counters with which to monitor performance. Don't forget that you need to get a baseline from your proxy server for later comparison. If you change hardware, OS, or proxy server parameters, don't forget to recalculate your baseline. The slightest change can throw your baseline completely off. Eventually, you'll get to know what the thresholds are for your proxy server environment and be able to plan accordingly.
Monitoring
Setting administrative alerts to point to serious Proxy Server events that demand immediate attention isn't an easy thing to do. In large shops supporting hundreds or thousands of proxy server users, you'll want to monitor multiple proxy servers and be alerted when specific conditions exist.
Performance Monitor works well to monitor specific counters looking for specific conditions or exceeding certain thresholds, but it isn't meant to be an enterprisewide monitoring tool. To obtain this comprehensive functionality, you must look to a third party. The crucial feature for monitors is their ability to monitor down to the service level. That means that you're looking not just for server failure, but also for service failure. Any product that provides this feature might also be able to provide other services, such as failure notifications by email or pager. The product might also attempt to restart the service automatically when a certain threshold is crossed. In many products, a number of options exist for reacting to a service-level failure.
I've used NetIQ AppManager (http://www.netiq.com/) in the past for service-failure functionality. Although AppManager is a pricey enterprise solution, it compensates for all Performance Monitor's shortcomings and can monitor a slew of different servers and platforms. Other products that perform this same functionality include Heroix's RoboMon (http://www.heroix.com/product_info.htm) and Argent Software's Guardian (http://www.argentsoftware.com/prod/product/guardian.htm).
The Future of Proxy Server
Over the past 7 months, I've explained how you can configure and optimize Proxy Server in your Web environment. As Proxy Server evolves into its next generation, I'll revisit this topic again from time to time. Meanwhile, be sure to check out the beta version of Microsoft's newest Internet product, Internet Security and Acceleration Server 2000 (http://www.microsoft.com/isaserver/default.asp). Internet Security and Acceleration Server 2000 has many roots in Proxy Server 2.0. This version requires that you run Win2K Server, Win2K Advanced Server, or Win2K Datacenter Server.
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