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 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 exceedsfcl_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.
fcl_keeptime
Specifies the maximum amount of space that can be
allocated to the VxFS File Change Log (FCL). The FCL
file is a sparse file that grows as changes occur in the
file system. When the space allocated to the FCL file
reaches the fcl_maxalloc value, the oldest FCL
records 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 file system
runs out of space before fcl_maxalloc is reached,
the FCL is deactivated.
The minimum value of fcl_maxalloc is 4 MB. The
default value is fs_size/33.
Either or both of the fcl_maxalloc or
fcl_keeptime parameters must be set before the
File Change Log can be activated. fcl_maxalloc
does not apply to disk lay out Versions 1 through 5.
fcl_maxalloc
VxFS performance: creating, mounting, and tuning file systems
Tuning I/O
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