Windows Server Tuning Parameters

• Know what /3GB parameter means?
• Do you only see 4GB RAM while you actually have 8GB?
• TCP tuned for optimal network throughput under load?

Windows Kernel  Network  Disk I/O  Disable Services Not In Need

Windows Kernel

User-mode vs. Kernel Memory

By default Windows 2003 server kernel run in a 2GB memory space.  For a Windows server that is dedicated to a particular application, 2GB kernel maybe too large.  It is certainly feasible to reduce it to 1GB and leave more physical memory for your application(s).

Microsoft Windows provides a /3GB parameter to be added to the BOOT.INI file that reallocates 3 GB of memory to be available for user-mode applications and reduces the amount of memory for the system kernel to 1 GB. Many enterprise databases, such as DB2 and Oracle, can derive performance benefits from having large amounts of addressable memory available for creating agent processes that handle a large number of concurrent database connections.

To edit the BOOT.INI file to make this change, complete the following steps:
1. Open the System Control Panel.
2. Select the Advanced tab.
3. In the Startup and Recovery frame, click the Settings button.
4. Click Edit. Notepad opens to edit the current BOOT.INI file.
5. Edit the current ARC path to include the /3GB switch in the same line that has /fastdetect.
6. Restart the server for the change to take affect.

Physical Address Extension (PAE)

The native 32-bit architecture of the x86 processor allows a maximum addressable memory space of 4 GB (2^32). The Intel Physical Address Extension (PAE) is a 36-bit memory addressing mode that allows 32-bit systems to address memory above 4 GB. PAE requires appropriate hardware and operating system support to be implemented. Intel introduced PAE 36-bit physical addressing with the Intel Pentium® Pro processor. Windows supported PAE since Windows NT Server 4.0 Enterprise Edition, and it is supported with the Advanced and Datacenter Editions of Windows Specify "/PAE" in boot.ini to allow full use of 8GB physical RAM.

To edit the BOOT.INI file to make this change, complete the following steps:
1. Open the System Control Panel.
2. Select the Advanced tab.
3. In the Startup and Recovery frame, click the Settings button.
4. Click Edit. Notepad opens to edit the current BOOT.INI file.
5. Edit the current ARC path to include the /PAE switch in the same line that has /fastdetect.
6. Restart the server for the change to take affect.

Network

Gigabit-based network interfaces have many performance-related parameters inside of their device driver such as CPU affinity.  In addition, the TCP protocol can be tuned to increase network throughput for connection-hungry applications.  For Windows servers, use the both the network adapter properties and Windows registry to update the TCP layer parameters. If your environment is uniformly Windows platform, make sure all these parameters are set to the same values across all your servers:

Tune TCP

Offloading Checksum

Network adapter (such as Broadcomm) that implements Network Driver Interface Specification (NDIS) task offload allows offloading checksum calculation to the network adapter hardware. Because checksum calculation is the most expensive function in the networking stack, doing so offers a significant performance advantage by reducing the number of system CPU cycles required per byte. Offload as many tasks shown in your network adapter. The following screen shows an example offloading task configured for our test system:

In addition, the property "Jumbo MTU" stands for the support of jumbo frames with a specified Maximum Transmission Unit (MTU). Data (or files) being transport through your network cards are broken into MTUs. If your MTU is small (default 1500), more packets will have to be processed, therefore, under heavy load, cpu can be high, and throughput can decrease. If your application deals with large files (500K+ bytes), it is always recommended to turn on the Jumbo MTU support and set it to 9000. But note, you can set Jumbo MTU on your server to be 9k, but if your network switch does NOT support jumbo frames, then you are still actully using MTU=1500 (the lower of the two). So make sure you ask your network admin about the Jumbo Frames support on the network switch that your server(s) connect to.

Disk I/O

Tune Disk Performance

Microsoft has a very good article on monitoring and tune disk I/O on Windows server systems: http://www.microsoft.com/technet/prodtechnol/Windows2000Pro/reskit/part6/proch30.mspx.
 

Some disk tuning suggestions from the article - "if your disk system is too slow, consider the following alternative steps:
- Rule out a memory shortage. When memory is scarce, the Virtual Memory Manager writes more pages to disk, resulting in increased disk activity. Because low memory is a common cause of bottlenecks, make sure that this is not the source of the problem before adding hardware. Also, make sure to set the paging file to an appropriate size as described in "Evaluating Memory and Cache Usage" in this book.
- Defragment the disk using Disk Defragmenter. For information about using Disk Defragmenter, see Windows 2000 Help.
- Use Diskpar.exe on the Windows 2000 Resource Kit companion CD to reduce performance loss due to misaligned disk tracks and sectors.
- Use striped volumes to process I/O requests concurrently over multiple disks. The type you use depends on your data-integrity requirements. Implement striped volumes for fast reading and writing and improved storage capacity. When striped volumes are used, disk utilization per disk need to fall due to distribution of work across the volumes and overall throughput need to increase. When using striped volumes, make sure to use the optimal size of stripe for your workload. The stripe size needs to be a multiple of the size of the average request. If you find that there is no increased throughput when scaling to additional disks in a striped volume, you might be experiencing a bottleneck due to contention between disks for the disk adapter. You might need to add an adapter to better distribute the load.
- Place multiple drives on separate I/O buses, particularly if a disk has an I/O-intensive workload.
- Distribute workload among multiple drives. For example, for database applications, you might want to put transaction logs on a separate spindle from data. Notice that writing to a log file is a sequential operation and tends to be more efficient than the random operations typical of accessing data in a database. If you are unsure of a suitable distribution for network applications, track users and the files they work with in order to plan an efficient distribution by means of the auditing capability of the NTFS file system. This tells you which disks are getting the most usage and helps you determine whether you need to redistribute workloads. For more information about auditing, see Windows 2000 Professional Help.
- Limit your use of file compression or encryption. These features can add some overhead and you need to use them sparingly if not required by your enterprise and if performance is critical.
- When obtaining disk systems, use the most intelligent and efficient components available for your disk system, including controller, I/O bus, cabling, and the disk. Upgrade to faster-speed or wider-bandwidth components as necessary. These measures generally decrease transfer time and improve throughput. Use intelligent drivers that support interrupt moderation or interrupt avoidance to alleviate the interrupt activity for the processor due to disk I/O. Some graphs can be used for the disk monitoring page for clarity.

Disable Unused Services

When Windows is first installed, many services are enabled that may not be necessary for a particular server. Inexperienced users may also inadvertently add additional services that are not actually required for a given system. Each service requires system resources and as a result it is best to disable non-required services to improve performance.  Some recommended services to disable.  Do the update in the Services panel: 1. Right-click My Computer and select Manage. 2. Expand the Services and Applications icon. 3. Select the Services icon.