netapp cifs 2.1

For more information, please view the following URL: https://kb.netapp.com/support/index?page=content&actp=LIST&id=7010114
Summary
Two critical issues have been discovered in the lease functionality of the SMB 2.1 protocol supported in Data ONTAP operating in 7-Mode. These issues have the potential to cause disruptions in CIFS service availability. NetApp recommends upgrading to new releases where key issues are addressed. If you still experience issues, NetApp recommends disabling SMB 2.1 for specific releases to temporarily address these issues. Clients can still connect to NetApp storage using SMB 2.0.

The lease functionality impacts some users with newer clients (Windows 7 or newer, Windows Server 2008 R2 or newer) interacting with NetApp storage controllers.

Impacted Data ONTAP Releases (7-Mode) for BURT 720236

·         8.1.2P3 and later P-releases
·         8.1.3 and all P-releases
·         8.2 and all P-releases

Impacted Data ONTAP Releases (7-Mode) for BURT 798842

·         8.1.2P3 and later P-releases
·         8.1.3 and all P-releases
·         8.1.4 and 8.1.4P1
·         8.2 and all P-releases
·         8.2.1RC1 and RC2

Problem Description
Two critical issues have been identified (BUG: 720236 and BUG 798842) in the above mentioned Data ONTAP 7-Mode releases that have the potential to cause controller disruption. Please see the public report for the above mentioned Bug IDs for more details.

In order to avoid the risk of disruption, follow the recommended workaround and solution in the sections, below.
Workaround
To address most common occurrence of this issue via BUG 720236, customers running impacted Data ONTAP Releases in 7-Mode should upgrade to 8.1.4 (or newer) or 8.2.1 RC2 to avoid this issue.

For those who cannot upgrade or for those that also encounter a rare occurrence of disruptions due to Bug ID 798842, NetApp recommends disabling SMB 2.1 for specific releases to temporarily address these issues. Clients can still connect to NetApp storage using SMB 2.0 and maintain the many benefits SMB 2.0 provides.

Instructions to disable SMB 2.1 manually:

filer> priv set diag; setflag smb_enable_2_1 0; priv set
Note: this affects all CIFS services on the controller, across all vFilers

To make this persistent over reboots, run the command below:
filer> wrfile -a /etc/rc “priv set diag; setflag smb_enable_2_1 0; priv set”

Verify the changes in the /etc/rc file:
filer> rdfile /etc/rc

Note: Disabling SMB 2.1 affects new connections only. Future connections will negotiate at the SMB 2.0 protocol level.

If you need to be absolutely certain that all clients are negotiating SMB 2.0, terminating and restarting CIFS after disabling SMB 2.1 is an option.
Note: This operation is service-disrupting.

Run the following commands to terminate and restart CIFS after manually disabling SMB2.1:
For customers with MultiStore:
filer> vfiler run * cifs terminate -t 0; vfiler run * cifs restart

For customers without MultiStore:
filer> cifs terminate -t 0; cifs restart
Solution
The fix for Bug ID 720236 is included in Data ONTAP 7-Mode 8.1.4 (or newer) and 8.2.1 RC2.
The fix for rarely occurring Bug ID: 798842 is planned to be delivered in the near future.
 
Information on leases in SMB 2.1 from Microsoft TechNet:
“The introduction of the client oplock leasing model in SMB 2.1 allows opportunistic locks to be held by a client over a wider range of scenarios. This feature offers enhanced file caching and metadata (file information) caching opportunities for the SMB client, and brings major performance benefits by limiting the amount of data that needs to be transferred between the client computer and the server. This enhancement particularly benefits networks with high latency.”

Source
Additional Information
BUG 720236
BUG 798842