For restoring to multiple files:
gbak {-C|-R} [options] source primary m secondary1 [ n1 secondary2 [ n2]]

database: Name of a database to back up or restore.

source: Name of a storage device or backup file from which to restore.
On UNIX, this can also be stdin, in which case gbak reads input
from the standard input (usually a pipe).

target: Name of a storage device or backup file to which to back up.
On UNIX, this can also be stdout, in which case gbak writes its
output to the standard output (usually a pipe).

primary Primary file when restoring to multiple database files.

m Length of primary in database pages; minimum value is 200.

secondary1 First secondary file when restoring to multiple database files.

n1 Length of secondary1; if only one secondary file is supplied, n1 is
optional.

secondary2 Next secondary file; specify as many secondary files as needed.

n2 Length of secondary2; it is unnecessary to specify the length of the
last secondary file.

Насчет второго - теоретически 16 Тб, практически я не доходил :) Думаю, 200-300 потянет