Veritas Storage Foundation™ for Oracle 5.0.1 Administrator's Guide

The preferred write request size. The file system uses this
parameter in conjunction with the write_nstream value
to determine how to do flush behind on writes. The default
value is 64K.
write_pref_io
The number of parallel read requests of size read_pref_io
that you can have outstanding at one time. The file system
uses the product of read_nstream multiplied by
read_pref_io to determine its read ahead size. The default
value for read_nstream is 1.
read_nstream
The number of parallel write requests of size
write_pref_io that you can have outstanding at one time.
The file system uses the product of write_nstream
multiplied by write_pref_io to determine when to do
flush behind on writes. The default value for
write_nstream is 1.
write_nstream
Any file I/O requests larger than the
discovered_direct_iosz are handled as discovered
direct I/O. A discovered direct I/O is unbuffered similar to
direct I/O, but does not require a synchronous commit of
the inode when the file is extended or blocks are allocated.
For larger I/O requests, the CPU time for copying the data
into the page cache and the cost of using memory to buffer
the I/O data becomes more expensive than the cost of doing
the disk I/O. For these I/O requests, using discovered direct
I/O is more efficient than regular I/O. The default value of
this parameter is 256K.
discovered_direct_iosz
Tuning for performance
About tuning VxFS
304