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What's New in SMB in Windows Server


Applies To: Windows Server 2012 R2

This topic introduces the new features and functionality for Server Message Block (SMB) in Windows Server 2012 R2.

Server Message Block (SMB) is a network file sharing protocol that allows applications on a computer to read and write to files and to request services from server programs in a computer network.

For an overview description of SMB, see Server Message Block Overview.

What’s new in SMB in Windows Server 2012 R2

The following table describes the new features and improvements for SMB 3.0 in Windows Server 2012 R2.


New or updated


Automatic rebalancing of Scale-Out File Server clients


This functionality improves scalability and manageability for Scale-Out File Servers. SMB client connections are tracked per file share (instead of per server), and clients are then redirected to the cluster node with the best access to the volume used by the file share. This improves efficiency by reducing redirection traffic between file server nodes. Clients are redirected following an initial connection and when cluster storage is reconfigured.

Improved performance of SMB Direct (SMB over RDMA)


Improves performance for small I/O workloads by increasing efficiency when hosting workloads with small I/Os (such as an online transaction processing (OLTP) database in a virtual machine). These improvements are evident when using higher speed network interfaces, such as 40 Gbps Ethernet and 56 Gbps InfiniBand.

Improved SMB event messages


SMB events now contain more detailed and helpful information. This makes troubleshooting easier and reduces the need to capture network traces or enable more detailed diagnostic event logging. By default, the most relevant event channels are turned on, so you instantly capture all of the essential information. In addition, some events now include details on configuration and troubleshooting solutions.

VHDX files as shared storage for guest clustering


Simplifies the creation of guest clusters by using shared VHDX files for shared storage inside the virtual machines. You can use this feature with VHDX files that are stored in Cluster Shared Volumes (CSV) or SMB Scale-Out file shares. For more information, see Deploy a Guest Cluster Using a Shared Virtual Hard Disk.

Hyper-V Live Migration over SMB


Enables you to perform a live migration of virtual machines by using SMB 3.0 as a transport. This allows you to take advantage of key SMB features, such as SMB Direct and SMB Multichannel, by providing high speed migration with low CPU utilization.

Improved SMB bandwidth management


Enables you to configure SMB bandwidth limits to control different SMB traffic types. There are three SMB traffic types: default, live migration, and virtual machine.

Support for multiple SMB instances on a Scale-Out File Server


Provides an additional instance on each cluster node in Scale-Out File Servers specifically for CSV traffic. A default instance can handle incoming traffic from SMB clients that are accessing regular file shares, while another instance only handles inter-node CSV traffic. This feature improves scalability and reliability of traffic between CSV nodes.

SMB 1.0 is now an optional feature


The SMB 1.0 features, including the legacy computer browser service and Remote Administration Protocol (RAP), are now separate and can be eliminated. These features are still enabled by default, but if you have no older SMB clients, such as Windows XP or Windows Server 2003, you can remove the SMB 1.0 features to increase security and potentially reduce patching.

See also