VERITAS File System 4.1 Administrator's Guide

VxFS Performance: Creating, Mounting, and Tuning File Systems
I/O Tuning
Chapter 260
default_indir_
size
On VxFS, files can have up to ten direct extents of variable
size stored in the inode. Once these extents are used up, the
file must use indirect extents which are a fixed size that is
set when the file first uses indirect extents. These indirect
extents are 8K by default. The file system does not use
larger indirect extents because it must fail a write and
return ENOSPC if there are no extents available that are the
indirect extent size. For file systems with many large files,
the 8K indirect extent size is too small. The files that get
into indirect extents use many smaller extents instead of a
few larger ones. By using this parameter, the default
indirect extent size can be increased so large that files in
indirects use fewer larger extents. The tunable
default_indir_size should be used carefully. If it is set
too large, then writes will fail when they are unable to
allocate extents of the indirect extent size to a file. In
general, the fewer and the larger the files on a file system,
the larger the default_indir_size can be set. This
parameter should generally be set to some multiple of the
read_pref_io parameter. default_indir_size is not
applicable on Version 4 and Version 5 disk layouts.
fcl_keeptime Specifies the minimum amount of time, in seconds, that the
VxFS file change log (FCL) keeps records in the log. When
the oldest 8K block of FCL records have been kept longer
than the value of fcl_keeptime, they are purged from the
FCL and the extents, nearest to the beginning of the FCL
file are freed. This process is referred to as "punching a
hole." Holes are punched in the FCL file in 8K chunks.
If the fcl_maxalloc parameter is set, records are purged
from the FCL if the amount of space allocated to the FCL
exceeds fcl_maxalloc, even if the elapsed time the records
have been in the log is less than the value of fcl_keeptime.
If the file system runs out of space before fcl_keeptime is
reached, the FCL is deactivated.
Either or both of the fcl_keeptime or fcl_maxalloc
parameters must be set before the file change log can be
activated. fcl_keeptime does not apply to disk layout
Versions 1 through 5.