The target_block_size specifies the logical block size in bytes of the new filesystem. Valid target block sizes for the s5 filesystem are 512, 1024, and 2048. The default target block size for the s5 filesystem is 2048.
The fsba command prints information about how many 512-byte disk sectors are allocated to store the data in the old (existing) filesystem and how many would be required to store the same data in a new filesystem with the specified logical block size. It also prints the number of allocated and free i-nodes for the existing filesystem.
If the number of free sectors listed for the new filesystem is negative, the data will not fit in the new filesystem unless the new file system is larger than the existing filesystem. The new filesystem must be made at least as large as the number of sectors listed by fsba as allocated for the new filesystem. The maximum size of the new filesystem is limited by the size of the disk partition used for the new filesystem.
Note that it is possible to specify a target_block_size that is smaller than the logical block size of the existing filesystem. In this case the new filesystem would require fewer sectors to store the data.