Veritas™ File System 5.0.1 Administrator's Guide

Table 2-1
Tunable VxFS I/O parameters (continued)
DescriptionParameter
On VxFS, files can have up to ten direct extents of variable
size stored in the inode. After these extents are used up,
the file must use indirect extents which are a fixed size
that is set when the file first uses indirect extents. These
indirect extents are 8K by default. The file system does
not use larger indirect extents because it must fail a write
and return ENOSPC if there are no extents available that
are the indirect extent size. For file systems with many
large files, the 8K indirect extent size is too small. The
files that get into indirect extents use many smaller
extents instead of a few larger ones. By using this
parameter, the default indirect extent size can be
increased so large that files in indirects use fewer larger
extents. The tunable default_indir_ size should be
used carefully. If it is set too large, then writes fail when
they are unable to allocate extents of the indirect extent
size to a file. In general, the fewer and the larger the files
on a file system, the larger the default_indir_ size
can be set. This parameter should generally be set to some
multiple of the read_pref_io parameter.
default_indir_ size is not applicable on Version 4
disk layouts.
default_indir_ size
Enables or disables caching on Quick I/O files. The default
behavior is to disable caching. To enable caching, set
qio_cache_enable to 1. On systems with large
memories, the database cannot always use all of the
memory as a cache. By enabling file system caching as a
second level cache, performance may be improved. If the
database is performing sequential scans of tables, the
scans may run faster by enabling file system caching so
the file system performs aggressive read-ahead on the
files.
qio_cache_enable
VxFS performance: creating, mounting, and tuning file systems
Tuning I/O
58