NBU will scan the file system and find all files, and if the file system driver/plugin for the archiving system is configured correctly to exclude backup programs for fetching the archived file, NBU would only backup up the stub file.
If you haven't set up the correct access policy, you could potentially end up with backing up your archive, and with Centera you would probably get ~3MB/s, if accessed through DiskX or a Celerra. An archived file generally doesn't have to be backed up, you should have backed it up before being archived. Centera does support DR backup, but it is too slow to be of any use. EMC, I think, have come up with a new solution, but I'm not sure if the backup performance has improved...
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