Become superuser or assume an equivalent role on the cluster node you want to back up.
Estimate the size of the backup in bytes.
# ufsdump S filesystem
Displays the estimated number of bytes needed to perform the backup.
Specifies the name of the file system you want to back up.
Divide the estimated size by the capacity of the tape to see how many tapes you need.
In the following example, the file system size of 905,881,620 bytes will easily fit on a 4 GB tape (905,881,620 ÷ 4,000,000,000).
# ufsdump S /global/phys-schost-1 905881620