PRIMECLUSTER Global File Services Configuration and Administration Guide 4.2 (Solaris(TM) Operating Environment)

8.1 Defragmentation Function

If many files are repeatedly created and deleted in the GFS Local File System, the extents allocated to the files and free extents of the file system may be fragmented and dispersed. This state is referred to as fragmentation. If the file system becomes highly fragmented, the device seek time overhead may increase, and file access performance may be adversely affected.

The GFS Local File System enables defragmentation for eliminating these fragments.

Defragmentation makes contiguous the fragmented extents allocated to the files and changes the storage locations of file extents to create large free areas in the file system.

The following results can be expected by defragmentation:

• Insufficient meta-data areas in the file system can be eliminated by making the fragmented extents contiguous.
• File access efficiency can be improved by making the fragmented extents contiguous.

The following operations cannot be performed if defragmenting in the mounted state (online):

- File system cannot be unmounted (umount(1M)).

- File system size cannot be extended (sfxadd(1M)).
The following operations cannot be performed if defragmenting in the unmounted state (offline):

- File system cannot be mounted (mount(1M)).

- File system size cannot be extended (sfxadd(1M)).

- File system integrity cannot be recovered (fsck(1M)).

- Files cannot be manipulated.

Similarly, in the unmounted state (offline), if an option enabling disk quotas in /etc/vfstab have been specified, defragmantation is performed but the disk quotas are not enabled. As a result, if disk quotas are enabled after offline defragmentation has been performed, quota data is updated.