Citrix: 7.6 PVS: Reducing Network Utilization

Reducing Network Utilization

http://support.citrix.com/proddocs/topic/provisioning-7/pvs-network-utilization-reduce.html#pvs-network-utilization-reduce

Windows provides several features that presume the use of a large, fast hard-disk.

While many of these features can also be useful on a diskless system where the disk is actually on the network, using them decreases cache effectiveness and thereby increases network utilization. In an environment that is sensitive to network utilization, consider reducing the effect of these features by disabling them or adjusting their properties.

In particular, System Restore and Offline Folders are not useful on a diskless system and can be detrimental to the performance of Windows on a diskless system. Provisioning Services provides a clearer, more reliable, and simpler restore point than System Restore by simply rebooting the target device. Offline Folders cache network files — a feature that is not applicable to a system where all files are on the network.

All of these features are configurable through the target device itself (for details, refer to configurable through the target device). The following features are configurable in the Windows Group Policy.

  • Offline Folders
  • Event Logs

Configuring Windows features on a Standard vDisk

  1. Prepare a Standard Image vDisk for configuration.
    • Shutdown all target devices that use the Standard Image vDisk.
    • From the Console, change the Disk Access Mode to Private Image.
    • Boot one target device.
  2. Configure one or more features.
  3. Prepare the Standard Image vDisk for use
    • Shutdown the target device previously used to configure the vDisk.
    • From the Console, change the Disk Access Mode to Standard Image.
    • Boot one or more target devices.

Configuring the Recycle Bin

Disabling the Recycle Bin deletes files immediately. Consequently, the file system reuses respective disk sectors and cache entries sooner.

To configure the Recycle Bin:

  1. From the target device, or Windows Explorer, right click on the Recycle Bin.
  2. Select Properties.
  3. Select Global.
  4. Select from the following settings:
    • Use one setting for all drives
    • Do not move files to the Recycle Bin. Remove files immediately when deleted.

Configuring Offline Folders

The disabling of Offline Folders is strongly recommended to prevent Windows from caching network files on its local disk – a feature with no benefit to a diskless system. Configure this feature from the target device or Windows Group Policy.

To configure from the target device:

  1. Open Windows Explorer.
  2. Select Tools>Folder Options.
  3. Select Offline Folders.
  4. Uncheck Enable Offline Folders.

To configure using the Windows Group Policy:

On the domain controller, use the Microsoft Management Console with the Group Policy snap-in, to configure the domain policies for the following:

Object User ConfigurationAdministrative TemplatesNetworkOffline Files
Policy

Setting

Disable user configuration of offline files

Enabled

Policy

Setting

Synchronize all offline files before logging off

Disabled

Policy

Setting

Prevent use of the Offline Files folder

Enabled

Configuring Event Logs

Reduce the maximum size of the Application, Security, and System logs. Configure this feature using the target device or Windows Group Policy.

To configure event logs, on the target device:

  1. Select Start>Settings>Control Panel.
  2. Open Administrative Tools>Event Viewer.
  3. Open the properties for each log.
  4. Set the Maximum log size to a relatively low value. Consider 512 kilobytes.

To configure using the Windows Group Policy:

On the domain controller, use the Microsoft Management Console with the Group Policy snap-in to configure the domain policies for the following object:

Object Computer ConfigurationWindows SettingsEvent LogSettings for Event Logs
Policy

Setting

Policy Maximum Application Log Size

Relatively low value. Consider 512 kilobytes.

Policy

Setting

Maximum Security Log Size

Relatively low value. Consider 512 kilobyte.

Policy

Setting

Maximum System Log Size

Relatively low value. Consider 512 kilobytes.

Configuring System Restore

The disabling of System Restore is strongly recommended to prevent Windows XP from storing any restore points that result in large disk files. Provisioning Services provides an inherent restore feature whenever the target device reboots.

On Windows XP, disable System Restore:

  1. Select Start, then Control Panel.
  2. Open System.
  3. Select System Restore.
  4. Check Turn off System Restore.

Configuring Logical Prefetch

Disabling Logical Prefetcher prevents Windows XP from caching additional files.

To disable logical prefetcher, set the following registry value to 0 (zero):

HKLMSYSTEMCurrentControlSetControlSession ManagerMemory ManagementPrefetchParametersEnablePrefetcher

Configuring Automatic Disk Defragmentation

Disabling Automatic Disk Defragmentation prevents Windows XP from filling the vDisk write cache by automatically de-fragmenting the vDisk during boot time.

To disable automatic disk defragmentation, set the following registry key value data:

Key HKEY_LOCAL_MACHINEMicrosoftDfrgBootOptimizeFunction

Value Name Enable

Value Type REG_SZ

Value Data N

Disabling Windows Automatic Updates

If you have the Windows Automatic Updates service running on your target device, Windows periodically checks a Microsoft Web site and looks for security patches and system updates. If it finds updates that have not been installed, it attempts to download them and install them automatically. Normally, this is a useful feature for keeping your system up-to-date. However, in a Provisioning Services implementation using Standard Image mode, this feature can decrease performance, or even cause more severe problems. This is because the Windows Automatic Updates service downloads programs that fill the write cache. When using the target device’s RAM cache, filling the write cache can cause your target devices to stop responding.

Re-booting the target device clears both the target device and Provisioning Services write cache. Doing this after an auto-update means that the Automatic Updates changes are lost, which defeats the purpose of running Automatic Updates. (To make Windows updates permanent, you must apply them to a vDisk while it is in Private Image mode).

To prevent filling your write cache, make sure to disable the Windows Automatic Updates service for the target device used to build the vDisk.

To disable the Windows Automatic Updates feature:

  1. Select Start>Settings>Control Panel>Administrative Tools.
  2. Select System.
  3. Click the Automatic Updates tab.
  4. Select the Turn Off Automatic Updates radio button.
  5. Click Apply.
  6. Click OK.
  7. Select Services.
  8. Double-click the Automatic Updates service.
  9. Change the Startup Type by selecting Disabled from the drop-down list.
  10. If the Automatic Updates service is running, click the Stop button to stop the service.
  11. Click OK to save your changes.
To make Windows updates permanent:

  1. Shutdown all target devices that share the vDisk.
  2. Change the vDisk mode to Private image.
  3. Boot one target device from that vDisk.
  4. Apply Windows updates.
  5. Shutdown the target device.
  6. Change vDisk mode to Standard image.
  7. Boot all target devices that share this vDisk.
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