Veritas Storage Foundation for Oracle 5.0 Administrator's Guide, HP-UX 11i v3, Second Edition, December 2008

To increase space, you could perform a volume relayout using the vxrelayout
command. However, changing a large volume from a four-way striped volume to
six-way striped volume involves moving old block information into temporary
space and writing those blocks from the temporary space to a new volume, which
takes a long time. To solve this problem, Veritas Storage Foundation for Oracle
offers a new feature called a Load Balanced File System (LBFS).
An LBFS is created on a multi-volume file system where individual volumes are
not striped over individual disks. For data-availability, these individual volumes
can be mirrored. The file system on the LBFS has a special placement policy called
a balance policy. When the balance policy is applied, all the files are divided into
small "chunks" and the chunks are laid out on volumes so that adjacent chunks
are on different volumes. The default chunk size is 1MB and can be modified.
Since every file contains chunks on all available volumes, it is important that
individual volumes that make up the LBFS and volume set be of same size and
same access properties. Setting up the file system in this way provides the same
benefit as striping your volumes. Use the dbdst_makelbfs command to create an
LBFS file system. Note that you cannot convert an existing file system to an LBFS
file system.
Extent balancing file system
You can define allocation policies with a balance allocation order and "chunk"
size to files or a file system, known as extent balancing. The chunk size is the
maximum size of any extent that files or a file system with this assigned policy
can have. The chunk size can only be specified for allocation policies with a balance
allocation order.
An extent balancing policy specifies the balance allocation order and a non-zero
chunk size. The balance allocation order distributes allocations randomly across
the volumes specified in the policy and limits each allocation to a maximum size
equal to the specified chunk size.
Extent balancing extends the behavior of policy enforcement by rebalancing
extent allocations such that each volume in the policy is as equally used as possible.
Policy enforcement handles the following cases:
■ New volumes are added to the policy, and the extents associated with a file
need rebalancing across all volumes, including the new ones.
■ Volumes are removed from the volume set or from the policy, and the extents
for a file residing on a removed volume need to be moved to other volumes in
the policy.
■ An extent balancing policy is assigned to a file and its extents have to be
reorganized to meet the chunk size requirements defined in the policy.
Using Database Dynamic Storage Tiering
Extent balancing in a database environment
198