ONTAP 8.3 and later does NOT use node_mgmt LIF for external services such as DNS, LDAP etc.

In Data ONTAP 8.3 or later, each SVM initiates outbound connections to name servers using its own LIFs and routes, not those of the node_mgmt LIF as in previous releases.

IMPORTANT information for ONTAP 8.3 and later customers:
SVMs (vserver) lacking a specific route, and also having multiple default routes containing the same routing metric (possibly from separate routing groups before the upgrade) could fail to reach the name servers if any of the specified gateways do not provide a path to those servers as the node_mgmt_LIF can no longer be used to reach such services.

Protocols that could be affected:
Any protocol that relies on name services (LDAP, NIS, DNS, Active Directory) is susceptible, for example : NFS and CIFS data protocols are particularly susceptible.


Symptoms:
1. CIFS: clients cannot reach share names.
2. AD: SVM fails to join AD.
3. NFS: Clients cannot mount exports that include host-names instead of IP.

Workaround/Solution:
1. If each gateway can reach all name services, then no changes are needed.
2. Ensure that the correct default route with access to all names services has the lowest metric.
3. Create a specific routing group and add a specific route to the destination.


Courtesy: KBID:1000317

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.

Go for ONTAP 9.3 minimum: iSCSI Performance Improvements

If iSCSI is your MAIN SAN protocol, then you must think about upgrading your controllers to 9.3 minimum:

Reason: The entire iSCSI stack was re-written for ONTAP 9.3. This was done to increase parallelization so that iSCSI processing could take advantage of the higher core controllers that NetApp has been shipping recently.

Prior to the re-write some iSCSI processing was single threaded and therefore had a bottleneck where processing was dependent on the speed of a single processor core. By refactoring the NetApp software iSCSI target to multi-threaded iSCSI processing iSCSI (ONTAP 9.3) is now able to take advantage of numerous CPU cores each of which can concurrently process iSCSI threads.

In addition, increasing multi-threading, other improvements, while perhaps not as substantial, were also included. These include reducing or eliminating locks and context switches and other incremental improvements. The improvements in iSCSI performance seen from this refactoring of iSCSI software target are substantial with the largest improvements seen on larger controllers that have more cores that can be used to concurrently process iSCSI threads.

Compared to 9.2: 2.6x Performance increase @1ms

TR:4080

Just one page is enough to understand How NetApp File System Magic works.

https://www.usenix.org/legacy/event/usenix08/tech/full_papers/edwards/edwards_html/netapp2008-flexvols.html