SMB 1.0 is disabled by default in ONTAP 9.3

For environments with existing CIFS servers running SMB 1.0,  migrate to a later SMB version as soon as possible to get best of security and compliance enhancements.


Microsoft extended support has ended for SMB 1.0 :
Windows 2000                   (July 13, 2010)
Windows XP                      (April 8, 2014)
Windows Server 2003 R2 (July 14, 2015)


In ONTAP 9, 9.1,   SMB = Enabled by default
In ONTAP 9.2,       SMB = Can be disabled
In ONTAP 9.3,       SMB = Disabled by-default


Advantage in ONTAP 9.x:

SMB 2.1 Large MTU: allows SMB’s maximum transmission unit (MTU) to be increased from 64KB (default) to 1MB. Doing so significantly improves the speed and efficiency of large file transfers while reducing the number of packets that need to be processed. This approach enables customers using 10-gigabit Ethernet to take advantage of their high-bandwidth networks.

command:
cifs options modify -is-large-mtu-enabled true


When disabled (the default setting), NetApp® ONTAP® software advertises max read and write sizes as 64K.

NOTE: Do not confuse it with Network MTU, SMB MTUs do not refer to MTU sizes used at the network layer.