Another way to tune CPU performance is to use Task Manager to identify processes that are consuming the most CPU time, then adjust the priority of those processes. A process starts with a base priority level, and its threads can deviate two levels higher or lower than the base. If you have a busy CPU, you can boost a process's priority level to improve CPU performance for that process. To do so, press Ctrl+Alt+Del to access Task Manager, then go to the Processes tab. Right-click the process, choose Set Priority, and select a value of High, Normal, or Low, as Figure 4 shows. The priority change takes effect immediately, but this fix is temporary: After you reboot the system or stop and start the application, you'll lose the priority properties that you set. To ensure that an application always starts at a specified priority level, you can use the Start command from the command line or within a batch script. To review the Start command's options, enter
start /?
at the command prompt.
Disk
To determine whether your system is experiencing disk bottlenecks, first ensure that the problem isn't occurring because of insufficient memory. A disk bottleneck is easy to confuse with pagefile activity resulting from a memory shortage. To help you distinguish between disk activity related to Virtual Memory Manager's paging to disk and disk activity related to applications, keep pagefiles on separate, dedicated disks.
Before you use Performance Monitor to examine your disks, you must understand the difference between its two disk counters. LogicalDisk counters measure the performance of high-level items (e.g., stripe sets, volume sets). These counters are useful for determining which partition is causing the disk activity, possibly identifying the application or service that's generating the requests. PhysicalDisk counters show information about individual disks, regardless of how you're using the disks. LogicalDisk counters measure activity on a disk's logical partitions, whereas PhysicalDisk counters measure activity on the entire physical disk.
NT doesn't enable Performance Monitor disk counters by default; you must enable them manually. Enabling these counters will result in a 2 to 5 percent performance hit on your disk subsystem. To activate Performance Monitor disk counters on the local computer, type
diskperf -y
at a command prompt. (If you're monitoring RAID, use the -ye switch.) Restart the computer.
To analyze disk-subsystem performance and capacity, monitor the Performance Monitor's disk-subsystem counters. The following counters are available under both LogicalDisk and PhysicalDisk:
- % Disk Time—Measures the amount of time the disk spends servicing read and write requests. If this value is consistently close to 100 percent, the system is using the disk heavily. If the disk is consistently busy and a large queue has developed, the disk might be experiencing a bottleneck. Under typical conditions, the value should be 50 percent or less.
- Avg. Disk Queue Length—Shows the average number of pending disk I/O requests. If this value is consistently higher than 2, the disk is experiencing congestion.
- Avg. Disk Bytes/Transfer—Measures throughput (i.e., the average number of bytes transferred to or from the disk during write or read operations). The larger the transfer size, the more efficiently the system is running.
- Disk Bytes/sec—Measures the rate at which the system transfers bytes to or from the disk during write or read operations. The higher the average, the more efficiently the system is running.
- Current Disk Queue Length—Shows how many disk requests are waiting for processing. During heavy disk access, queued requests are common; however, if you see requests consistently backed up, your disk isn't keeping up.
If you determine that your disk subsystem is experiencing a bottleneck, you can implement several solutions. You can add a faster disk controller, add more disk drives in a RAID environment (spreading the data across multiple physical disks improves performance, especially during reads), or add more memory (to increase file cache size). You also might try defragmenting the disk, changing to a different I/O bus architecture, placing multiple partitions on separate I/O buses (particularly if a disk has an I/O-intensive workload), or choosing a new disk with a low seek time (i.e., the time necessary to move the disk drive's heads from one data track to another). If your file system is FAT, remember that NTFS is best for volumes larger than 400MB.
You can also provide more disk spindles to the application. How you organize your data depends on your data-integrity requirements. Use striped volumes to process I/O requests concurrently across multiple disks, to facilitate fast reading and writing, and to improve storage capacity. When you use striped volumes, disk utilization per disk decreases and overall throughput increases because the system distributes work across the volumes.
Consider matching the file system's allocation unit size to the application block size to improve the efficiency of disk transfers. However, increasing the cluster size doesn't always improve disk performance. If the partition contains many small files, a smaller cluster size might be more efficient. You can change the cluster size in two ways. At the command line, enter
format <disk>:/FS:NTFS /A:<cluster size>
or use Disk Administrator. Select Tools, Format, and change the allocation unit size. NTFS supports a cluster size of 512 bytes, 1024 bytes, 2048 bytes, 4096 bytes, 8192 bytes, 16KB, 32KB, or 64KB. FAT supports a cluster size of 8192 bytes, 16KB, 32KB, 64KB, 128KB, or 256KB.
Network Interface
After you consider a system's memory, CPU, and disk metrics, your next step is to examine the network subsystem. Client machines and other systems must be able to connect quickly to the NT Server system's network I/O subsystem so that they provide acceptable response times to end users. To determine where network bottlenecks reside and how to fix them, you must understand what type of workload your client systems generate, which key network architecture components are in use, and what type of network protocol (e.g., Ethernet, NetBEUI) and physical network you're on. Performance Monitor collects data for each physical network adapter. To determine how busy your adapters are, use the following counters:
- Network Interface: Output Queue Length—Measures the length of an adapter's output packet queue. A value of 1 or 2 is acceptable. However, if this measurement is frequently at or higher than 3 or 4, your network I/O adapter can't keep up with the server's requests to move data onto the network.
- Network Interface: Bytes Total/sec—Measures all network traffic (number of bytes sent and received) that moves through a network adapter, including all overhead that the network protocol (e.g., TCP/IP, NetBEUI) and physical protocol (e.g., Ethernet) incur. If, for example, in a 10Base-T network, the value is close to 1Mbps and the output queue length continues to increase, you might have a network bottleneck.
- Network Interface: Bytes Sent/sec—Shows the number of bytes sent through a specific network adapter card.
- Server: Bytes Total/sec—Shows the number of bytes that the server has sent and received over the network through all of its network adapter cards.
- Server: Logon/sec—Shows the number of logon attempts per second for local authentication, over-the-network authentication, and service-account authentication. This counter is useful on domain controllers (DCs) to determine how much logon validation is occurring.
- Server: Logon Total—Shows the number of logon attempts for local authentication, over-the-network authentication, and service-account authentication since the computer was last started.
If you determine that the network subsystem is experiencing a bottleneck, you can implement numerous measures to alleviate the problem. You can bind your network adapter to only those protocols that are currently in use, upgrade your network adapters to the latest drivers, upgrade to better adapters, or add adapters to segment the network (so that you can isolate traffic to appropriate segments). Check overall network throughput, and improve physical-layer components (e.g., switches, hubs) to confirm that the constraint is in the network plumbing. You might also try distributing the processing workload to additional servers.
In a TCP/IP network, you can adjust the TCP window size for a potential improvement in performance. The TCP/IP receive window size shows the amount of receive data (in bytes) that the system can buffer at one time on a connection. In NT, the window size is fixed and defaults to 8760 bytes for Ethernet, but you can adjust the window size in the registry. You can either modify the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\ Parameters\TcpWindowSize subkey to globally change the setting on the computer or use the setsockopt() Windows Sockets call to change the setting on a per-socket basis. The optimal size depends on your network architecture. In TCP, the maximum achievable throughput equals window size divided by round-trip delay or network latency.
Finally, don't use Autosense mode in your network adapters. Set your NICs to the precise speed that you want. To change the setting, use the configuration program that came with your network adapter.
Understand Your Environment
Performance analysis requires logical thinking, testing, and patience. NT's primary monitoring and tuning tools can help you manage the performance of your company's systems.
The key to achieving your objective is understanding what you have, how your applications work, and how your users use your network. To resolve any performance problems and plan for future requirements, combine the knowledge you gain from these tools' output with an understanding of your applications and your environment.
End of Article
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