NDMP DUMP methods, walking inode file Vs logical traversal

There are two methods dump uses to determine which file goes into a dump - the "walking inode file" path and the "logical traversal" path. 

Walking inode file: This approach goes through all the inodes in the inode file and decides which file goes into the dump.

Logical traversal :This approach does a logical traversal on the subtree to be dumped. When dumping a qtree tree, the first approach is used. 

However, under the certain conditions, it becomes more expensive to do "walking inode file" than "logical traversal".

For example - When the volume has a lot of used inodes; and The qtree is very small relative to the size of the volume it resides in.

In Cluster data ontap or ONTAP 9, you can determine which method dump is currently set to by entering the following command -

cluster_ontap_9::*> vserver services ndmp show -vserver vserver_name

This switch determines the two methods as shown in figure below.
switch = [-dump-logical-find <text>] (privilege: advanced)

This option mentioned above, specifies whether to follow inode-file walk or tree walk for phase I of the dump. Choosing inode-file walk or tree walk affects the performance of the dump.

This option [-dump-logical-find <text>] can take following values:

If default is specified [which is the default setting], then level 0 and incremental volume as well as qtree dumps will use inode walk.

If always is specified, all the subtree dumps will use tree walk, and all dumps will follow treewalk.