Skip to main content

Configuring SMB Multichannel for performance and redundancy

Beginning in ONTAP 9.4, you can configure SMB Multichannel to provide multiple connections between ONTAP and clients in a single SMB session. Doing so improves throughput and fault tolerance.

Before you begin

You can use SMB Multichannel functionality only when clients negotiate at SMB 3.0 or later versions. SMB 3.0 and later is enabled on the ONTAP SMB/CIFS server by default.

About this task

SMB clients automatically detect and use multiple network connections if a proper configuration is identified on the ONTAP cluster.

The number of simultaneous connections in an SMB session depends on the NICs you have deployed:

1G NICs on client and ONTAP cluster
The client establishes one connection per NIC and binds the session to all connections.
10G and larger capacity NICs on client and ONTAP cluster
The client establishes up to four connections per NIC and binds the session to all connections. The client can establish connections on multiple 10G and larger capacity NICs.

You can also modify the following parameters (advanced privilege):

-max-connections-per-session
The maximum number of connections allowed per Multichannel session. The default is 32 connections.
If you want to enable more connections than the default, you must make comparable adjustments to the client configuration, which also has a default of 32 connections.
-max-lifs-per-session
The maximum number of network interfaces advertised per Multichannel session. The default is 256 network interfaces.
  1. Set the privilege level to advanced: set -privilege advanced
  2. Enable SMB Multichannel on the SMB/CIFS server: vserver cifs options modify -vserver vserver_name -is-multichannel-enabled true
  3. Verify that ONTAP is reporting SMB Multichannel sessions: vserver cifs session show options
  4. Return to the admin privilege level: set -privilege admin

The following example displays information about all SMB/CIFS sessions, showing multiple connections for a single session:

cluster1::> vserver cifs session show
Node:    node1
Vserver: vs1
Connection Session                                        Open            Idle
IDs        ID      Workstation      Windows User         Files            Time      
---------- ------- ---------------- ---------------- --------- ---------------
138683,
138684,
138685     1       10.1.1.1         DOMAIN\                   0              4s          
                                    Administrator

The following example displays detailed information about an SMB/CIFS session with session-id 1:

cluster1::> vserver cifs session show -session-id 1 -instance

Vserver: vs1
                           Node: node1
                     Session ID: 1
                 Connection IDs: 138683,138684,138685
               Connection Count: 3
   Incoming Data LIF IP Address: 192.1.1.1
         Workstation IP Address: 10.1.1.1
       Authentication Mechanism: NTLMv1
          User Authenticated as: domain-user
                   Windows User: DOMAIN\administrator
                      UNIX User: root
                    Open Shares: 2
                     Open Files: 5
                     Open Other: 0
                 Connected Time: 5s
                      Idle Time: 5s
               Protocol Version: SMB3
         Continuously Available: No
              Is Session Signed: false
                   NetBIOS Name: -