Identifying Potential Bottlenecks

Deviations from your baseline provide the best indicator of performance problems. However, as a secondary reference, the following table describes recommended thresholds for object counters. Use this table to help you identify when a performance problem is developing on your system. If the values listed are consistently reported on your system, consult additional chapters in the Performance Monitoring section of this book for how to investigate and correct the problems causing these values.

Table 5.8 Recommended Thresholds for the Minimum Set of System Counters

Resource	Object\Counter	Suggested threshold	Comments
Disk	LogicalDisk\% Free Space	15 percent	None
Disk	LogicalDisk\% Disk Time	90 percent	None
Disk	PhysicalDisk\ Disk Reads/sec, PhysicalDisk\ Disk Writes/sec	Depends on manufacturer's specifications	Check the specified transfer rate for your disks to verify that this rate does not exceed the specifications. In general, Ultra Wide SCSI disks can handle 50 to 70 I/O operations per second.
Disk	PhysicalDisk\ Current Disk Queue Length	Number of spindles plus 2	This is an instantaneous counter; observe its value over several intervals. For an average over time, use PhysicalDisk\Avg. Disk Queue Length.
Memory	Memory\ Available Bytes	Less than 4 MB	Research memory usage and add memory if needed.
Memory	Memory\ Pages/sec	20	Research paging activity.
Network	Network Segment\% Net Utilization	Depends on type of network	You must determine the threshold based on the type of network you are running. For Ethernet networks, for example, 30 percent is the recommended threshold.
Paging File	Paging File\% Usage	Above 70 percent	Review this value in conjunction with Available Bytes and Pages/sec to understand paging activity on your computer.
Processor	Processor\% Processor Time	85 percent	Find the process that is using a high percentage of processor time. Upgrade to a faster processor or install an additional processor.
Processor	Processor\ Interrupts/sec	Depends on processor; for current CPUs, use a threshold of 1500 interrupts per second.	A dramatic increase in this counter value without a corresponding increase in system activity indicates a hardware problem. Identify the network adapter or disk controller card causing the interrupts. You might need to install an additional adapter or controller card.
Server	Server\Bytes Total/sec		If the sum of Bytes Total/sec for all servers is roughly equal to the maximum transfer rates of your network, you might need to segment the network.
Server	Server\Work Item Shortages	3	If the value reaches this threshold, consider tuning the InitWorkItems or MaxWorkItems entries in the registry (in HKEY_LOCAL_MACHINE \SYSTEM\CurrentControlSet \Services\lanmanserver\Parameters). For more information about MaxWorkItems, see the Microsoft Knowledge Base link on the Web Resources page at http://windows.microsoft.com /windows2000/reskit/webresources Caution Do not use a registry editor to edit the registry directly unless you have no alternative. The registry editors bypass the standard safeguards provided by administrative tools. These safeguards prevent you from entering conflicting settings or settings that are likely to degrade performance or damage your system. Editing the registry directly can have serious, unexpected consequences that can prevent the system from starting and require that you reinstall Windows 2000. To configure or customize Windows 2000, use the programs in Control Panel or Microsoft Management Console whenever possible.
Server	Server Work Queues\Queue Length	4	If the value reaches this threshold, there might be a processor bottleneck. This is an instantaneous counter; observe its value over several intervals.
Multiple Processors	System\Processor Queue Length	2	This is an instantaneous counter; observe its value over several intervals.

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