Veritas File System 5.1 SP1 Administrator"s Guide (5900-1499, April 2011)

Table 2-1
Tunable VxFS I/O parameters (continued)
DescriptionParameter
Specifies the minimum size to qualify a deleted inode
for inode aging. Inode aging is used in conjunction
with file system Storage Checkpoints to allow quick
restoration of large, recently deleted files. For best
performance, it is advisable to age only a limited
number of larger files before completion of the
removal process. Setting the size too low can push
larger file inodes out of the aging queue to make room
for newly removed smaller file inodes.
inode_aging_size
The maximum size of a direct I/O request that are
issued by the file system. If a larger I/O request comes
in, then it is broken up into max_direct_iosz
chunks. This parameter defines how much memory
an I/O request can lock at once, so it should not be set
to more than 20 percent of memory.
max_direct_iosz
Limits the maximum disk queue generated by a single
file. When the file system is flushing data for a file
and the number of pages being flushed exceeds
max_diskq, processes are blocked until the amount
of data being flushed decreases. Although this does
not limit the actual disk queue, it prevents flushing
processes from making the system unresponsive. The
default value is 1 MB.
max_diskq
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 because the algorithm tries
to double the size of the file with each new extent. As
such, 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 262144 blocks,
which prevents one filefrom holding too much unused
space. max_seqio_extent_size is measured in file
system blocks. The default and minimum value of this
parameter is 2048 blocks.
max_seqio_extent_size
59VxFS performance: creating, mounting, and tuning file systems
Tuning I/O