Veritas Storage Foundation for Oracle 5.0 Graphical User Interface Guide, HP-UX 11i v3, First Edition, May 2008

if your database block size is 32K and your file system block size is 8k, VxFS can
put four 8K blocks together to perform one 32K database I/O operation.
When creating the file system, set the number of file system blocks in the intent
log so that the log size is 16MB. For example, if the file system block size is 8K
(that is, 8192), it will take 2000 blocks to make a 16MB log (2000 x 8192 = ~16MB).
If the file system block size is 4K (that is, 4096), then twice as many blocks as in
the 8K case would need to be allocated (4000 in this example).
For more about file systems and file system procedures, see the Veritas Enterprise
Administrator Guide.
For more about file systems and file system procedures, see the Volume Manager
Web GUI Online Help.
Controlling fragmentation
When free resources are initially allocated to files in a Veritas file system, they
are aligned in the most efficient order possible to provide optimal performance.
On an active file system, the original order is lost over time as files are created,
removed, or resized. As space is allocated and deallocated from files, the available
free space becomes broken into fragments. This means that space must be assigned
to files in smaller and smaller extents. This process is known as fragmentation.
Fragmentation leads to degraded performance and availability. The degree of
fragmentation depends on file system usage and activity.
Fragmentation utilities in VxFS
Allocation units in VxFS are designed to help minimize and control fragmentation.
Over time, however, file systems eventually become fragmented.
VxFS provides online reporting and optimization utilities to enable you to monitor
and defragment a mounted file system. These utilities are accessible through the
file system administration command, fsadm. Using the fsadm command, you can
track and eliminate fragmentation without interrupting user access to the file
system.
Types of fragmentation
VxFS addresses two types of fragmentation:
■ Directory fragmentation
As files are created and removed, gaps are left in directory inodes. This is
known as directory fragmentation. Directory fragmentation causes directory
lookups to become slower.
45Managing your database
Controlling fragmentation