Set cache size on local drive

Set cache size on local drive is a Windows Group Policy setting located under Computer Configuration > Policies > Administrative Templates > Windows Components > Delivery Optimization. It applies to the Computer Configuration branch and is classified as a Informational-level policy in the Delivery Optimization category.

Controls percentage of disk space used for caching downloaded updates. Higher cache reduces redundant downloads from peer devices.

Microsoft sets the default value to 20 while industry security baselines (CIS, NIST, DISA STIG) recommend 50.

Under the hood, this policy is enforced through the Windows registry at HKLM\Software\Policies\Microsoft\Windows\DeliveryOptimization using the value name CachePercent. Modifying the value directly through regedit.exe or PowerShell produces the same effect as configuring the GPO, but going through Group Policy is preferred so that the setting is centrally managed and survives reboots, image rebuilds, and policy refresh cycles.

This is primarily an operational or user-experience setting. It does not directly raise or lower the security posture, but it standardizes behavior across the fleet, which is important for predictable support, training, and troubleshooting in an MSP-managed environment.

The policy is grouped under Delivery Optimization, which means it is typically applied through a domain-wide GPO linked at the OU level. In a multi-tenant MSP context, scope it through WMI filters or security group filtering rather than linking at the domain root, so that you can roll out progressively (pilot OU → wider rings → all production).

The setting takes effect after the next Group Policy refresh (gpupdate /force for immediate testing, or by default within ~90 minutes for workstations and ~5 minutes on domain controllers). For computer-side policies a reboot may be required; for user-side policies, a sign-off/sign-on cycle is enough.

1. Open Group Policy Management Console (gpmc.msc) on a domain controller or a workstation with RSAT installed.
2. Create or edit a GPO linked to the OU containing the target computer configurations. We recommend a dedicated baseline GPO (e.g. SEC – Delivery Optimization) instead of editing Default Domain Policy.
3. Navigate to Computer Configuration > Policies > Administrative Templates > Windows Components > Delivery Optimization.
4. Open Set cache size on local drive and set it to 50.
5. Click OK and close the editor.
6. On the target endpoint, run gpupdate /force (or wait for the next refresh cycle), then verify with rsop.msc or gpresult /h report.html.

Direct registry path: HKLM\Software\Policies\Microsoft\Windows\DeliveryOptimization\CachePercent. You can apply the same change with PowerShell:

New-Item -Path 'HKLM\Software\Policies\Microsoft\Windows\DeliveryOptimization' -Force | Out-Null
Set-ItemProperty -Path 'HKLM\Software\Policies\Microsoft\Windows\DeliveryOptimization' -Name 'CachePercent' -Value <value> -Type DWord