clfs.sys

Windows Core Driver

System DriverSafeKernel

CPU Usage

0-3%

Memory

40-120 MB

Location

C:\Windows\System32\drivers

Publisher

Microsoft Corporation

Quick Answer

clfs-sys is a legitimate Windows kernel driver. It implements the Common Log File System to enable transactional logging and crash-safe operations at the OS level.

Is it a Virus?

✔ NO - Safe

Found in C:\Windows\System32\drivers\clfs.sys

Warning

Kernel drivers are essential; ensure signatures

Tampering or unexpected copies may indicate corruption

Can I Disable?

✔ ES

Disabling may affect crash recovery and logging features. Only disable if advised by Microsoft support

What is clfs.sys?

clfs-sys is the Windows Common Log File System driver that provides a structured, transactional logging framework for kernel-level file operations. It underpins consistent metadata updates, crash recovery logs, and reliable journaling across NTFS and other file systems.

CLFS.sys implements a kernel-mode log manager, enabling atomic writes and recoverable transactions. It coordinates log streams, ensures durability during crashes, and supports efficient retrieval of log records for system diagnostics.

Quick Fact: CLFS originated to improve reliability of file-system transactions and crash recovery in Windows, providing a scalable log-structured storage backend.

Types of CLFS-related Processes

Kernel Log Manager: Core service coordinating log records in kernel space
Log Consumer: Components that read log blocks for recovery or audit
Journal Writer: Writes transactional logs to persistent storage
Crash Dump Facilitator: Supports crash analysis by preserving logs

Is clfs-sys Safe?

Yes, clfs-sys is safe when it is the legitimate Microsoft system driver located in the expected path.

Is clfs-sys a Virus or Malware?

The authentic clfs-sys is not a virus. Malware may imitate names, so verify the digital signature and file path.

How to Tell if clfs-sys is Legitimate or Malware

File Location: Must be in C:\Windows\System32\drivers\clfs.sys. Any other location is suspicious.
Digital Signature: Right-click clfs.sys in File Explorer → Properties → Digital Signatures. Should show 'Microsoft Corporation' or 'Microsoft Windows'.
Version & Publisher: Open Details tab and ensure Publisher is 'Microsoft Windows' or 'Microsoft Corporation'.
System Integrity: Run sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth to confirm system integrity.

Red Flags: If clfs.sys is missing from the Windows driver folder, located in an unexpected path, unsigned, or replaced after updates, scan with Windows Defender and verify with Windows Update catalogs.

Why Is clfs-sys Running on My PC?

clfs-sys runs as part of the Windows logging framework. It starts at boot and remains loaded to support crash-safe file operations and transaction logging for multiple subsystems.

Reasons it's running:

System boot and driver initialization: Windows loads CLFS during startup to initialize the log framework used by file systems.
Kernel-level logging: CLFS coordinates transactional logs for file system operations in kernel mode.
Crash recovery readiness: The driver maintains logs used to reconstruct state after crashes or power loss.
Background diagnostics: CLFS logs events used by diagnostics and auditing services without user interaction.
System integrity checks: During file system checks or integrity scans, CLFS involvement ensures logs reflect operations.

Can I Disable or Remove clfs-sys?

Disabling is not recommended because CLFS is a core OS component essential to crash recovery and log integrity. Disabling may destabilize the system.

How to Stop clfs-sys

No supported manual stop: As a kernel driver, clfs-sys should not be stopped manually. System stability requires it.
Disable related features: Within Windows, there are no user-friendly switches to disable CLFS globally. Manage logging via analysis tools instead.
Safe mode testing: If troubleshooting, boot into Safe Mode to assess behavior without normal startup logging.

How to Uninstall Windows Components

✔ You cannot uninstall clfs-sys separately; it is a core OS driver. Windows updates provide fixes.
✔ If you suspect corruption, use Windows Update and system repair tools instead of removal.

Common Problems: High I/O or Driver Errors

If clfs-sys is implicated in I/O delays or kernel errors, address using OS repair and monitoring steps.

Common Causes & Solutions

Driver corruption or mismatch after faulty update: Run sfc /scannow and DISM to repair system files; apply the latest Windows updates.
Disk subsystem overload: Check disk health (chkdsk /f /r) and monitor I/O wait; close heavy I/O tasks.
Outdated OS: Update Windows to the latest build via Settings -> Update & Security -> Windows Update.
Conflicting startup services: Use MSConfig or Task Manager to disable non-essential startup services and third-party drivers.
Corrupt system logs: Clear and rebuild ETW/CLFS logs via system maintenance tools; avoid manual log deletion if unsure.
Security software interference: Temporarily disable third-party antivirus to test; ensure real-time protection is not blocking CLFS operations.

Quick Fixes:
1. Run System File Checker: open Command Prompt as Admin and run sfc /scannow
2. Run DISM: DISM /Online /Cleanup-Image /RestoreHealth
3. Update Windows to the latest build
4. Check Event Viewer for CLFS-related errors
5. If disk I/O is high, run CHKDSK /F /R on affected drives

Frequently Asked Questions

What is clfs-sys?

clfs-sys is the Windows Common Log File System kernel driver that provides transactional logging and crash-safe operations for the system.

Is clfs-sys a virus?

No. The legitimate clfs-sys is a Microsoft driver located in C:\Windows\System32\drivers. Verify its digital signature to confirm authenticity.

Where is clfs-sys located?

Typically in C:\Windows\System32\drivers\clfs.sys. Any other location is suspect and should be scanned.

Can I disable clfs-sys?

Disabling is not recommended as it is a core OS component. If needed for troubleshooting, seek guidance from Microsoft support.

Why is clfs-sys using CPU or memory?

As a kernel driver, CLFS is active during normal operation and logging. Low baseline usage is normal; spikes may indicate disk or logging activity, malware, or disk I/O bottlenecks.

How do I fix CLFS errors?

Run system repair tools (sfc /scannow, DISM), check disk health, review Event Viewer, and install the latest Windows updates. If problems persist, contact Microsoft support.