Find Storage Controller Filter Drivers in Registry

Windows catalogs filter drivers for storage controller buses within specific device class and enumeration keys inside the Windows Registry. By navigating the Registry Editor (regedit), administrators and developers can inspect, modify, or troubleshoot class-level and device-specific UpperFilters and LowerFilters that intercept I/O requests directed at storage controllers, host bus adapters (HBAs), and connected storage buses.

Class-Level Storage Controller Filter Drivers

Class-level filter drivers apply globally to all devices installed under the Storage Controller setup class. These drivers are cataloged in the Registry under the following path:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e97b-e325-11ce-bfc1-08002be10318}

Inside this key, look for the following values: * UpperFilters (REG_MULTI_SZ): Contains a list of drivers loaded above the storage controller class driver. * LowerFilters (REG_MULTI_SZ): Contains a list of drivers loaded below the class driver, directly above the bus or hardware miniport driver.

(Note: For legacy or standard IDE/ATA controllers, the relevant class key is {4d36e96a-e325-11ce-bfc1-08002be10318}.)

Device-Specific (Hardware Instance) Filter Drivers

Filter drivers can also be attached directly to a specific physical controller instance rather than the entire device class. These instance-specific filter drivers are located under the hardware enumeration tree:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\PCI\[VEN_xxxx&DEV_xxxx&...]\Device Instance ID

To locate the filter drivers for a specific bus or controller: 1. Expand the PCI or ACPI folder depending on how the storage controller bus is connected. 2. Locate the specific hardware instance ID for the controller. 3. Check the right-hand pane for UpperFilters or LowerFilters values attached directly to that device instance.

Locating the Filter Driver Service Definitions

The names listed in the UpperFilters and LowerFilters registry values correspond to service keys that define the actual driver binaries and their startup configurations. You can inspect the individual driver properties at:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\[FilterDriverName]

This location details the path to the driver file (ImagePath), its load type (Start), and the driver group dependencies.