VERITAS File System 4.1 Administrator's Guide

VxFS Performance: Creating, Mounting, and Tuning File Systems
I/O Tuning
Chapter 264
max_seqio_extent_
size
Increases or decreases the maximum size of an extent.
When the file system is following its default allocation
policy for sequential writes to a file, it allocates an initial
extent which is large enough for the first write to the file.
When additional extents are allocated, they are
progressively larger (the algorithm tries to double the size
of the file with each new extent) so each extent can hold
several writes worth of data. This is done to reduce the total
number of extents in anticipation of continued sequential
writes. When the file stops being written, any unused space
is freed for other files to use. Normally this allocation stops
increasing the size of extents at 2048 blocks which prevents
one file from holding too much unused space.
max_seqio_extent_size is measured in file system blocks.
qio_cache_enable 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 will
perform aggressive read-ahead on the files.