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

Table 2-1
Tunable VxFS I/O parameters (continued)
DescriptionParameter
Changes the default initial extent size. VxFS
determines, based on the first write to a new file, the
size of the first extent to be allocated to the file.
Normally the first extent is the smallest power of 2
that is larger than the size of the first write. If that
power of 2 is less than 8K, the first extent allocated
is 8K. After the initial extent, the file system increases
the size of subsequent extents with each allocation.
See max_seqio_extent_size.
Since most applications write to files using a buffer
size of 8K or less, the increasing extents start doubling
from a small initial extent. initial_extent_size
can change the default initial extent size to be larger,
so the doubling policy starts from a much larger initial
size and the file system does not allocate a set of small
extents at the start of file. Use this parameter only
on file systems that have a very large average file size.
On these file systems it results in fewer extents per
file and less fragmentation. initial_extent_size
is measured in file system blocks.
initial_extent_size
Specifies the maximum number of inodes to place on
an inode aging list. Inode aging is used in conjunction
with file system Storage Checkpoints to allow quick
restoration of large, recently deleted files. The aging
list is maintained in first-in-first-out (fifo) order up
to maximum number of inodes specified by
inode_aging_count. As newer inodes are placed
on the list, older inodes are removed to complete their
aging process. For best performance, it is advisable
to age only a limited number of larger files before
completion of the removal process. The default
maximum number of inodes to age is 2048.
inode_aging_count
The maximum buffer size allocated for file data; either
8K bytes or 64K bytes. Use the larger value for
workloads where large reads/writes are performed
sequentially. Use the smaller value on workloads
where the I/O is random or is done in small chunks.
8K bytes is the default value.
max_buf_data_size
VxFS performance: creating, mounting, and tuning file systems
Tuning I/O
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