Veritas™ File System 5.0.1 Administrator's Guide

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 buffers 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 file from
holding too much unused space.
max_seqio_extent_size is measured in file system
blocks. The default and minimum value of is 2048 blocks.
max_seqio_extent_size
57VxFS performance: creating, mounting, and tuning file systems
Tuning I/O