System information

Advanced Functions
5-27
• Capabilities at host to support LUN resizing
Proper LUN resizing depends on the capabilities of your operating system, partition editor, and file system utilities. It is
advised to check the related manuals and do some trial runs before doing LUN resizing for your production site. You may
use file system check utilities after the resizing for ensuring data integrity.
Below list the software that offers solutions to support partition resizing:
• Symantec Partition Magic : http://www.symantec.com/
• Paragon Partition Manager: http://www.paragon-software.com/
• Arconis Disk Director: http://www.acronis.com/
• Coriolis Systems iPartition (MAC OS): http://www.coriolis-systems.com/
There are also utilities offered by operating systems or file systems, and below are some examples:
• Windows 2003 server or later: DiskPart, see 5.5.6 Windows DiskPart Utility
• Linux ext2/ext3 file systems: resize2fs
• Linux ReiserFS file system: resize_reiserfs
• Linux XFS file system: xfs_growfs
• Linux GNU parted partition editor: http://www.gnu.org/software/parted/
• Symantec Veritas VxFS: fsadm and extendfs
Below are some commonly-seen restrictions regarding to file system and partition resizing:
• A LUN for resizing can have only one primary partition and no extended partition.
• A boot partition with operating system on it might not be shrunk
• Rebooting the OS might be needed after the resizing
• Resizing partition or file system might have to be done offline
• File system defragmentation might be needed before resizing
• Comparisons with thin provisioning
Dynamic LUN resizing is better than thin provisioning in terms of reliability and performance because it retains the linear
and contiguous data layout:
• Thin provisioning needs to maintain address translation tables, which could cause disastrous data loss when corrupted.
• The over-advertised capacity of thin provisioning misleads the space allocation algorithm of a file system.
• The scrambled data layout of thin provisioning cause bad performance, especially when sharing storage of different
types of workloads or host computers.
• Thin provisioning is very likely to be misled to allocate unnecessary space by data movement or data scrubbing
applications, like file system defragmentation.
5.5.1 Free chunk defragmentation
The free space on a disk group is managed as free chunks. When there is no logical disk on a disk group, all the available
space forms a free chunk. Later, free chunks are created when you delete logical disks or shrink the capacity of logical
disks, but adjacent free chunks will be merged automatically. You can use free chunks for creating new logical disks or
expanding a logical disk.
A logical disk has to use contiguous space on a disk group, so you need to merge all free chunks into one by the disk
group defragmentation utility, which starts a background task to move the data of all logical disks on the disk group to the
beginning space of the hard disks, such that all free space is consolidated to form single free chunk located at the ending
space of the hard disks. Two common scenarios are illustrated as below:
Note
The software listed above is only for your information; no warranty should be assumed. Please
contact the software vendors to learn how to use the software to support LUN resizing.