A chronic shortage of space usually results from having more users
on the system than the current hard disk can reasonably handle,
or simply having too many directories or files.
In either case, creating a new filesystem on a new hard disk
allows you to transfer some of the users and directories
from the primary hard disk to the new location,
freeing a significant amount of space on the existing filesystem
and improving system operation.
If free space is chronically low on your system, you might want to expand your system storage capacity by installing additional hard disks. See for more information. Once you partition the disk and create new slices with fdisk(1M) and disksetup(1M), you can use the added disk space or copy existing user or system directories to it.
If one filesystem is full and other filesystems have a significant
amount of free space (or there is additional unused space on the hard disk),
you can change the layout on the primary disk
to take advantage of the free space.
However, this procedure is not as simple as adding a second hard disk.
To change the number of filesystems on your hard disk or to reapportion the disk space among the filesystems: