I have a NAS that is used to store data from our LAN. For many years I've relied on tar or cpio to back up selected directories to tape. When I backup complete partitions or disks on the various computers I generally use dump as per the recommendation of W. Curtis Preston in UNIX Backup & Recovery.
I've recently decided to make one archival backup of the NAS, but it appears that dump does not work in my situation, possibly because of the format of the NAS. It is attached to our Linux or FreeBSD machines as a CIFS device at /media/nas, and the Windows ones as 'network storage' which I assume is SMB. It is a 2 Terabyte Buffalo Link Station. I would prefer to be able to use dump as per Preston's comparison of backup reliability, but will use cpio if no one can suggest a viable alternative.