- NDMP is not storage agnostic. In general you cannot backup data and restore to another array from another vendor or sometimes even another OS version.
- NDMP requries admin privileges. No problem for backups of large systems but not nice for restores, especially if a user want's to restore a single file.
- The majority of the backup software solutions do not index the files of the NDMP files. In TSM for example you can store a Table of Content (TOC) with the backup but if you want to restore a single file you have to load the TOC into a temporary table to work with it. This can be very time consuming.
- NDMP doesn't really support a incremental forever strategy. That means you have to do a full backup periodically which is a no go with large filesystems at petabyte scale that contain billion of files.