Boost Windows Server Performance: Essential Hotfixes for File Services

Table of Contents

File Services technologies are fundamental to managing storage, enabling data replication, managing shared folders, providing fast file searching, and facilitating access for diverse client operating systems, including UNIX-based computers. Maintaining optimal performance and stability for these services is critical in any Windows Server environment. This article outlines key hotfixes and updates specifically targeting File Services components on Windows Server 2012, Windows Server 2012 R2, Windows 8, and Windows 8.1 platforms.

Ensuring that your File Services components are up-to-date with the latest fixes is paramount for preventing potential issues, enhancing performance, and improving overall reliability. Microsoft periodically releases updates, including hotfixes, security patches, and feature rollups, that address known problems within these critical components. Applying these updates systematically helps maintain a robust and efficient file-serving infrastructure. The transition to a monthly rollup servicing model simplifies the update process significantly, allowing administrators to deploy a cumulative package of fixes. However, some specific fixes released before this model became standard may still be necessary and are listed for completeness.

Understanding the architecture of File Services, particularly the Server Message Block (SMB) and Network File System (NFS) protocols, is helpful in appreciating the impact of these updates. SMB is the native file-sharing protocol for Windows, while NFS is commonly used in mixed Windows and UNIX/Linux environments. Both rely on several interacting components and drivers within the operating system kernel and user space. Updates to these components often target specific scenarios involving high load, concurrent access, replication, or protocol-level interactions that could lead to performance degradation, errors, or instability.

Understanding Key File Services Components¶

Several core components work together to provide File Services functionality on Windows Server. Keeping these updated is crucial for performance and stability.

• SRV (Server): These drivers run on the server hosting the shared files. They handle incoming client requests over the network, process file operations, and interact with the local file system. srv.sys handles older SMB traffic, while srv2.sys handles SMB 2.0 and newer. srvnet.sys acts as an interface between the network stack and the file server. Updating these components is essential for server-side performance, scalability, and handling of client connections.
• MRXSMB (Multiple Redirector): These drivers run on the client computer accessing the shared files. They take file operation requests from applications, translate them into SMB protocol messages, and send them over the network to the server. mrxsmb.sys is the base mini-redirector, mrxsmb10.sys handles legacy SMB, and mrxsmb20.sys handles SMB 2.0/3.0. Updating these is important for client-side performance, connection stability, and correct protocol handling when accessing remote shares.
• RDBSS (Redirected Buffer Subsystem): This component provides a common interface for different network redirectors, including MRXSMB. It manages buffering and caching of data for remote file operations. Updates to rdbss.sys can impact the efficiency of data transfer between client applications and the network redirector.
• NTFS (New Technology File System): While not strictly a network File Service protocol component, NTFS is the primary file system used on Windows servers. Issues within the NTFS driver (ntfs.sys) can directly impact the performance and integrity of data stored locally and accessed remotely via SMB or NFS. Updates to NTFS often address file system corruption issues, performance bottlenecks, or crashes.
• NFS (Network File System): For environments using NFS, separate components are involved. Nfssvc.exe and Nfssvr.sys are server-side components, enabling Windows Server to share files with UNIX/Linux clients. Nfsclnt.exe, Nfsrdr.sys, and Nfsnp.dll are client-side components, allowing Windows clients to access shares hosted on NFS servers. Updates to these components are necessary for interoperability, performance, and stability in cross-platform file sharing.

Ideally, for comprehensive coverage, it is recommended to apply relevant updates for SRV, MRXSMB, and RDBSS components on both the server hosting the data and the client accessing it, especially in complex scenarios. However, at a minimum, the SRV components should be updated on the server and the MRXSMB/RDBSS components on the client.

Starting in October 2016, Microsoft adopted a monthly rollup model for updates. These rollups are cumulative and contain previously released fixes. Applying the latest monthly rollup is generally the recommended approach to ensure your system is current. However, some fixes released before this model was fully implemented (specifically before October 2016) might not be included in later rollups and are therefore still listed as specific recommendations. Always refer to the specific Knowledge Base (KB) article for details on which updates are superseded or included in rollups.

Essential Hotfixes and Updates for Windows Server 2012 and Windows 8¶

This section lists critical updates for File Services components on Windows Server 2012 and Windows 8 platforms. Keep in mind that applying a recent monthly rollup often supersedes many of these individual fixes.

For the most current SMB components, installing the following two updates is generally recommended:

• KB 2984005 - September 2014 update rollup for Windows RT, Windows 8, and Windows Server 2012. This rollup provides essential updates for various system components.
• KB 4520007 - October 8, 2019-KB4520007 (Monthly Rollup) or any later monthly rollup. This cumulative update incorporates a wide range of fixes, including updates to File Services components.

Let’s look at specific component updates:

NTFS Component (Windows Server 2012 / Windows 8)¶

• KB 3121255: Addresses a Stop error 0x00000024 that might occur in FsRtlNotifyFilterReportChange, potentially causing file copy operations to fail.
  • Reason: Contains an update for Ntfs.sys to resolve file system issues impacting stability and file operations.
  • Availability: Included in July 11, 2017-KB4025331 (Monthly Rollup) and later monthly rollups. Requires Windows 8 or Windows Server 2012.

SRV Component (Windows Server 2012 / Windows 8)¶

• KB 4493451: April 9, 2019-KB4493451 (Monthly Rollup).
  • Reason: Contains updated versions of srvnet.sys and srv2.sys (version 6.2.9200.22707) which include important fixes for server-side SMB handling.
  • Availability: Included in April 9, 2019-KB4493450 (Security-only update) and later monthly rollups.
• KB 2984005: September 2014 update rollup for Windows RT, Windows 8, and Windows Server 2012.
  • Reason: Includes the most current version of srvsvc.dll available at that time, addressing issues related to the Server service.
  • Availability: Requires Windows 8 or Windows Server 2012. This is an older rollup, superseded by later monthly rollups, but listed as a foundational update from its era.

MRXSMB Component (Windows Server 2012 / Windows 8)¶

• KB 4516055: September 10, 2019-KB4516055 (Monthly Rollup).
  • Reason: Contains updated versions of mrxsmb.sys (6.2.9200.22859), mrxsmb10.sys (6.2.9200.22702), and mrxsmb20.sys (6.2.9200.22365), providing critical fixes for client-side SMB redirector operations.
  • Availability: Included in September 10, 2019-KB4516062 (Security-only update) and later monthly rollups.

RDBSS Component (Windows Server 2012 / Windows 8)¶

• KB 4520007: October 8, 2019-KB4520007 (Monthly Rollup).
  • Reason: Includes the 6.2.9200.22874 version of rdbss.sys, addressing issues in the Redirected Buffer Subsystem for improved client-side performance and stability.
  • Availability: Included in October 8, 2019-KB4519985 (Security-only update) and later monthly rollups.

Essential Hotfixes and Updates for Windows Server 2012 R2 and Windows 8.1¶

This section details crucial updates for File Services components tailored for Windows Server 2012 R2 and Windows 8.1 platforms. As with the previous section, applying a recent monthly rollup is the primary method to obtain most of these fixes.

NTFS Component (Windows Server 2012 R2 / Windows 8.1)¶

• KB 3121255: Addresses a Stop error 0x00000024 in FsRtlNotifyFilterReportChange and potential file copy failures.
  • Reason: Contains an update for ntfs.sys (version 6.3.9600.18183) to resolve file system issues on these platforms.
  • Availability: Available via Windows Update. Included in May 9, 2017-KB4019215 (Monthly Rollup) and later monthly rollups. Requires Windows 8.1 or Windows Server 2012 R2 and KB 2919355 (April 2014 Update).

SRV Component (Windows Server 2012 R2 / Windows 8.1)¶

• KB 4493446: April 9, 2019-KB4493446 (Monthly Rollup).
  • Reason: Contains updated versions of srv.sys, srv2.sys, and srvnet.sys (version 6.3.9600.19309), providing significant fixes for server-side SMB operations and network interaction on these platforms.
  • Availability: Included in April 9, 2019-KB4493467 (Security-only update) and later monthly rollups.

MRXSMB Component (Windows Server 2012 R2 / Windows 8.1)¶

• KB 4525243: November 12, 2019-KB4525243 (Monthly Rollup).
  • Reason: Includes updated versions of client-side SMB redirector drivers: mrxsmb.sys (6.3.9600.19537), mrxsmb10.sys (6.3.9600.19293), and mrxsmb20.sys (6.3.9600.18586). These updates address various client-side issues when accessing SMB shares.
  • Availability: Included in November 12, 2019-KB4525250 (Security-only update) and later monthly rollups.

RDBSS Component (Windows Server 2012 R2 / Windows 8.1)¶

• KB 4520005: October 8, 2019-KB4520005 (Monthly Rollup).
  • Reason: Provides an updated version of rdbss.sys (6.3.9600.19481), bringing improvements to the Redirected Buffer Subsystem for better client performance and reliability on Windows 8.1 and Server 2012 R2.
  • Availability: Included in October 8, 2019-KB4519990 (Security-only update) and later monthly rollups.

Performance Tuning via Registry Keys¶

Beyond applying hotfixes, certain registry parameters can be adjusted to fine-tune SMB performance for specific workloads. While direct hotfixes often address bugs or specific performance issues, these keys allow administrators to modify default behavior.

• KB 2848322: Describes parameters like AsynchronousCredits for the LanmanServer service (HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanServer\Parameters\AsynchronousCredits) and ExtendedSessTimeout for the LanmanWorkstation service (HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\ExtendedSessTimeout).
  • Reason: These parameters can be adjusted to optimize the number of concurrent asynchronous SMB operations a server can handle or to modify session timeout behavior, potentially improving performance under high load or specific network conditions.
  • Note: Modifying registry parameters should be done with caution and thorough testing, as incorrect values can negatively impact system stability or performance. Consult the KB article for detailed guidance.

Services for NFS in Windows Server 2012 Environments¶

For environments requiring interoperability with UNIX/Linux clients via the Network File System (NFS) protocol, specific components and their updates are relevant.

NFS Server Components (Windows Server 2012 / Windows 8.0)¶

• KB 3130902: Addresses a Stop error 0x9E that can occur and prevents a failover cluster from coming online in Windows Server 2012.
  • Reason: Contains updated versions of Nfssvc.exe, Nfssvr.sys, and Msnfsflt.sys. These are critical updates for the stability and availability of the NFS server role, especially in clustered environments.
  • Availability: Available for individual download. Requires Windows Server 2012.

NFS Client Components (Windows Server 2012 / Windows 8.0)¶

• KB 3042826: Addresses a scenario where the POSIX subsystem might crash when attempting to create a Telnet session. While seemingly unrelated to NFS, this hotfix updates components that are part of the Services for NFS installation.
  • Reason: Contains updated versions of Psxdll.dll, Psxdllsvr.dll, Psxss.exe, and Posix.exe. These are components of the POSIX subsystem utilized by the NFS client.
  • Availability: Available for individual download. Requires Windows 8 or Windows Server 2012.

Services for NFS in Windows Server 2012 R2 Environments¶

Updates for NFS components on Windows Server 2012 R2 and Windows 8.1 environments.

NFS Server Components (Windows Server 2012 R2 / Windows 8.1)¶

• KB 4487016: February 19, 2019-KB4487016 (Preview of Monthly Rollup).
  • Reason: Includes updated versions of Nfssvc.exe (6.3.9600.18751) and Nfssvr.sys (6.3.9600.19240). These updates provide fixes for the NFS server service on Windows Server 2012 R2, improving its stability and performance.
  • Availability: Included in February 19, 2019-KB4487016 (Preview of Monthly Rollup) and later monthly rollups.
• KB 4503276: June 11, 2019-KB4503276 (Monthly Rollup).
  • Reason: Contains the 6.3.9600.19364 version of Rpcxdr.sys, a component used by NFS for Remote Procedure Call (RPC) external data representation. Updates to this can improve communication reliability.
  • Availability: Included in June 11, 2019-KB4503290 (Security-only update) and later monthly rollups.

NFS Client Components (Windows Server 2012 R2 / Windows 8.1)¶

• KB 4038792: September 12, 2017-KB4038792 (OS Build Monthly Rollup).
  • Reason: Includes updated versions of client-side NFS components: Nfsclnt.exe (6.3.9600.18751), Nfsrdr.sys (6.3.9600.18385), and Nfsnp.dll (6.3.9600.18384). These updates address issues affecting Windows clients accessing NFS shares, improving connectivity and file operation reliability.
  • Availability: Included in September 12, 2017-KB4038792 (OS Build Monthly Rollup) and later monthly rollups.

The Server Message Block (SMB) Model Explained¶

The Server Message Block (SMB) protocol is a fundamental part of Windows File Services. It operates on a client-server model, facilitating shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. Understanding its layers helps identify where performance issues might occur and which components are involved.

On the client side, user applications request operations on remote files. These requests pass through several layers:
1. User-mode applications initiate file operations.
2. The Redirected Buffer Subsystem (rdbss.sys) intercepts these requests, managing caching and buffering.
3. The SMB mini-redirector (mrxsmb.sys) translates the requests into SMB protocol messages. Different versions handle different SMB dialects: mrxsmb10.sys for legacy SMB, and mrxsmb20.sys for SMB 2.x and 3.x.
4. The SMB messages are sent over the network stack (TCP/IP).

On the server side, the process is reversed:
1. Incoming SMB requests are received by the network stack.
2. The SMB server components (srv.sys for legacy SMB, srv2.sys for SMB 2.x/3.x) and the network interface component (srvnet.sys) process the requests.
3. These components interact with the local file system, typically NTFS (ntfs.sys).
4. NTFS performs the requested operations on the local storage stack.
5. File system metadata and content can be cached in the system cache, managed by the kernel (ntoskrnl.exe).

The communication flow involves multiple driver layers in both the client and server kernels. Updates to any of these layers (rdbss.sys, mrxsmb*.sys, srv*.sys, ntfs.sys, srvnet.sys) can significantly impact the end-to-end performance, reliability, and security of SMB file sharing. Issues can arise from inefficient request processing, locking problems, caching bugs, or errors in protocol implementation.

Here is a simplified representation of the SMB model layers:

mermaid graph LR A[Application (Client)] --> B(RDBSS - rdbss.sys); B --> C(MRXSMB - mrxsmb*.sys); C --> D(Network Stack - TCP/IP); D -- Network --> E(Network Stack - TCP/IP); E --> F(SRVNET - srvnet.sys); F --> G(SRV - srv*.sys); G --> H(NTFS - ntfs.sys); H --> I(Storage Stack); I --> J(Physical Disk); Subgraph Client A B C D end Subgraph Server E F G H I J end
Figure: Simplified SMB Communication Flow

This diagram illustrates how a request from an application on the client traverses through redirector components, the network, server components, and finally the file system and storage.

Services for NFS Components Explained¶

Services for NFS provides an alternative file-sharing solution for environments that include UNIX or Linux systems. This service allows Windows servers to act as NFS servers or Windows clients to access NFS shares hosted elsewhere.

Key components of Services for NFS include:

• Server for NFS: This component, running on Windows Server, implements the NFS server protocol. It enables a Windows machine to export its file systems using NFS, making them accessible to NFS clients (typically UNIX/Linux). The main driver is Nfssvr.sys.
• Client for NFS: This component, available on Windows Server and Windows client OS (like Windows 8/8.1), implements the NFS client protocol. It allows a Windows machine to mount and access file systems shared by an NFS server. The main redirector driver is Nfsrdr.sys.

The communication model for NFS involves:
1. Client applications requesting file operations.
2. The Redirected Buffer Subsystem (Rdbss.sys) intercepts these requests.
3. The NFS mini-redirector (Nfsrdr.sys) translates requests into NFS protocol messages.
4. Messages are sent over the network (TCP/IP or UDP).
5. The NFS server (Nfssvr.sys) on the host processes incoming requests.
6. The NFS server interacts with the local file system (e.g., NTFS) to perform operations.

Similar to SMB, updates to the Nfssvr.sys and Nfsrdr.sys drivers, as well as underlying components like RDBSS or RPC (used by NFS), are crucial for interoperability, performance, and stability when using NFS.

Importance of Staying Updated¶

Applying the recommended hotfixes and rolling up updates is vital for several reasons:

• Performance Improvement: Many hotfixes directly address performance bottlenecks within the file system drivers or network protocol implementations. Applying these can lead to faster file access, reduced latency, and improved throughput.
• Stability and Reliability: Updates often fix bugs that can cause system crashes (Stop errors), service hangs, or data corruption. Applying these fixes enhances the overall stability and reliability of your file servers and clients.
• Data Integrity: Fixes related to file system drivers like NTFS ensure that data is written and read correctly, preventing potential corruption issues.
• Security: While this article focuses on performance and stability, many updates include security fixes for File Services components, protecting against vulnerabilities.
• Compatibility: Updates ensure compatibility with newer client operating systems, applications, and network infrastructure changes.

Adopting a consistent patching strategy, preferably utilizing the monthly rollup updates, is the most effective way to ensure your File Services components are current. Always test updates in a non-production environment before deploying them widely.

Regular maintenance, including applying these critical updates, is not just about fixing problems; it’s a proactive measure to prevent potential issues from impacting your operations. By keeping File Services components updated, you contribute significantly to the overall health, performance, and security of your Windows Server infrastructure.

What has been your experience managing File Services updates on Windows Server 2012 or 2012 R2? Have you encountered specific performance issues that were resolved by applying a hotfix or rollup? Share your thoughts and experiences in the comments below!