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Storage Foundation 7.4.1 Administrator's Guide - Linux

Last Published: 2019-09-25

Product(s): InfoScale & Storage Foundation (7.4.1)

Platform: Linux

Veritas File System File Change Log administrative interface

The File Change Log (FCL) can be set up and tuned through the fcladm and vxtunefs VxFS administrative commands.

See the fcladm(1M) and vxtunefs(1M) manual pages.

The FCL keywords for fcladm are as follows:

clear	Disables the recording of the audit, open, close, and statistical events after it has been set.
dump	Creates a regular file image of the FCL file that can be downloaded to an off-host processing system. This file has a different format than the FCL file.
on	Activates the FCL on a mounted file system. VxFS 5.0 and later releases support either FCL Versions 3 or 4. If no version is specified, the default is Version 4. Use fcladm on to specify the version.
print	Prints the contents of the FCL file starting from the specified offset.
restore	Restores the FCL file from the regular file image of the FCL file created by the dump keyword.
rm	Removes the FCL file. You must first deactivate the FCL with the off keyword, before you can remove the FCL file.
set	Enables the recording of events specified by the 'eventlist' option. See the `fcladm`(1M) manual page.
state	Writes the current state of the FCL to the standard output.
sync	Brings the FCL to a stable state by flushing the associated data of an FCL recording interval.

The FCL tunable parameters for vxtunefs are as follows:

fcl_keeptime	Specifies the duration in seconds that FCL records stay in the FCL file before they can be purged. The first records to be purged are the oldest ones, which are located at the beginning of the file. Additionally, records at the beginning of the file can be purged if allocation to the FCL file exceeds fcl_maxalloc bytes. The default value of fcl_keeptime is 0. If the fcl_maxalloc parameter is set, records are purged from the FCL file if the amount of space allocated to the FCL file exceeds fcl_maxalloc. This is true even if the elapsed time the records have been in the log is less than the value of fcl_keeptime.
fcl_maxalloc	Specifies the maximum number of spaces in bytes to be allocated to the FCL file. When the space allocated exceeds fcl_maxalloc, a hole is punched at the beginning of the file. As a result, records are purged and the first valid offset (fc_foff) is updated. In addition, fcl_maxalloc may be violated if the oldest record has not reached fcl_keeptime. The minimum value of fcl_maxalloc is 4 MB. The default value is fs_size/33.
fcl_winterval	Specifies the time in seconds that must elapse before the FCL records an overwrite, extending write, or a truncate. This helps to reduce the number of repetitive records in the FCL. The fcl_winterval timeout is per inode. If an inode happens to go out of cache and returns, its write interval is reset. As a result, there could be more than one write record for that file in the same write interval. The default value is 3600 seconds.
fcl_ointerval	The time interval in seconds within which subsequent opens of a file do not produce an additional FCL record. This helps to reduce the number of repetitive records logged in the FCL file. If the tracking of access information is also enabled, a subsequent file open even within the fcl_ointerval may produce a record, if it is opened by a different user. Similarly, if the inode is bumped out of cache, this may also produce more than one record within the same open interval. The default value is 600 sec.

Either or both fcl_maxalloc and fcl_keeptime must be set to activate the FCL feature. The following are examples of using the fcladm command.

To activate FCL for a mounted file system, type the following:

  # fcladm on mount_point

To deactivate the FCL for a mounted file system, type the following:

  # fcladm off mount_point

To remove the FCL file for a mounted file system, on which FCL must be turned off, type the following:

  # fcladm rm mount_point

To obtain the current FCL state for a mounted file system, type the following:

  # fcladm state mount_point

To enable tracking of the file opens along with access information with each event in the FCL, type the following:

  # fcladm set fileopen,accessinfo mount_point

To stop tracking file I/O statistics in the FCL, type the following:

  # fcladm clear filestats mount_point

Print the on-disk FCL super-block in text format to obtain information about the FCL file by using offset 0. Because the FCL on-disk super-block occupies the first block of the FCL file, the first and last valid offsets into the FCL file can be determined by reading the FCL super-block and checking the fc_foff field. Enter:

  # fcladm print 0 mount_point

To print the contents of the FCL in text format, of which the offset used must be 32-byte aligned, enter:

  # fcladm print offset mount_point