Expanding a File System Using the growfs Command

After a volume that contains a file system is expanded (more space is added), if that volume contains a UFS, you also need to “grow” the file system to recognize the added space. You must manually grow the file system with the growfs command. The growfs command expands the file system, even while mounted. However, write access to the file system is not possible while the growfs command is running.

An application, such as a database, that uses the raw device must have its own method to grow added space. Solaris Volume Manager does not provide this capability.

The growfs command will “write-lock” a mounted file system as it expands the file system. The length of time the file system is write-locked can be shortened by expanding the file system in stages. For instance, to expand a 1 Gbyte file system to 2 Gbytes, the file system can be grown in 16 Mbyte stages using the -s option to specify the total size of the new file system at each stage.

During the expansion, the file system is not available for write access because of write-lock. Write accesses are transparently suspended and are restarted when the growfs command unlocks the file system. Read accesses are not affected, though access times are not kept while the lock is in effect.

Background Information for Expanding Slices and Volumes

Solaris Volume Manager volumes can be expanded, but not shrunk.

• A volume, regardless if it is used for a file system, application, or database, can be expanded. So, you can expand RAID 0 (stripe and concatenation) volumes, RAID 1 (mirror) volumes, and RAID 5 volumes as well as soft partitions.

• You can concatenate a volume that contains an existing file system while the file system is in use. Then, as long as the file system is UFS, it can be expanded (with the growfs command) to fill the larger space without interrupting read access to the data.

• Once a file system is expanded, it cannot be shrunk, due to constraints in UFS.

• Applications and databases that use the raw device must have their own method to “grow” the added space so that they can recognize it. Solaris Volume Manager does not provide this capability.

• When a component is added to a RAID 5 volume, it becomes a concatenation to the device. The new component does not contain parity information. However, data on the new component is protected by the overall parity calculation that takes place for the volume.

• You can expand a log device by adding additional components. You do not need to run the growfs command, as Solaris Volume Manager automatically recognizes the additional space on reboot.

• Soft partitions can be expanded by adding space from the underlying volume or slice. All other volumes can be expanded by adding slices.

How to Expand a File System

Steps

1. Check Prerequisites for Creating Solaris Volume Manager Components.

2. Use the growfs command to grow a UFS on a logical volume.

   # growfs -M /mount-point /dev/md/rdsk/volumename

   See the following example and the growfs(1M) man page for more information.

Example 22–5 Expanding a File System

# df -k
Filesystem            kbytes    used   avail capacity  Mounted on
...
/dev/md/dsk/d10        69047   65426       0   100%    /home2
...
# growfs -M /home2 /dev/md/rdsk/d10
/dev/md/rdsk/d10:       295200 sectors in 240 cylinders of 15 tracks, 82 sectors
        144.1MB in 15 cyl groups (16 c/g, 9.61MB/g, 4608 i/g)
super-block backups (for fsck -F ufs -o b=#) at:
 32, 19808, 39584, 59360, 79136, 98912, 118688, 138464, 158240, 178016, 197792,
 217568, 237344, 257120, 276896,
# df -k
Filesystem            kbytes    used   avail capacity  Mounted on
...
/dev/md/dsk/d10       138703   65426   59407    53%    /home2
...

In this example, a new slice was added to a volume, d10, which contains the mounted file system /home2. The growfs command specifies the mount point with the -M option to be /home2, which is expanded onto the raw volume /dev/md/rdsk/d10. The file system will span the entire volume when the growfs command is complete. You can use the df -hk command before and after to verify the total disk capacity.

For mirror and transactional volumes, always run the growfs command on the top-level volume, not a submirror or master device, even though space is added to the submirror or master device.