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defragment(8)							defragment(8)



NAME

  defragment - Makes the files in a file domain	more contiguous

SYNOPSIS

  /usr/sbin/defragment [-e] [-n] [-N threads] [-t time]	[-T time] [-v] [-V]
  domain

OPTIONS

  -e  Ignores errors and continues, if possible. Errors	that are ignored are
      usually related to a specific file.

  -N threads
      Specifies	the number of threads to run on	the utility.  The default
      number of	threads	that will be run is the	number of volumes in the
      domain.  The maximum number you can specify for the number of threads
      is 20.

  -n  Prevents defragmentation from actually taking place. Use in conjunction
      with the -v option to display statistics on the number of	extents	in
      the file domain.

  -t time
      Specifies	a flexible time	interval (in minutes) for the defragment
      utility to run. If the utility is	performing an operation	when the
      specified	time has elapsed, the procedure	continues until	the operation
      is complete.

  -T time
      Specifies	an exact time interval (in minutes) for	the defragment util-
      ity to run. When the specified time has elapsed, the defragmentation
      procedure	stops, even if it is performing	an operation.

  -v  Displays statistics on the amount	of fragmentation in the	file domain
      and information on the progress of the defragment	procedure.

  -V  Displays the same	information provided by	the -v option along with
      information about	each operation the defragment utility performs on
      each file.  This option slows the	defragment procedure.

OPERANDS

  domain
      Specifies	the name of the	file domain.








DESCRIPTION

  When a file consists of many discontiguous file extents, the file is frag-
  mented on the	disk. File fragmentation reduces the read/write	performance
  because more I/O operations are required to access a fragmented file.

  The defragment utility attempts to reduce the	number of file extents in a
  file domain by making	files more contiguous. Defragmenting a file domain
  often	makes the free space on	a disk more contiguous,	resulting in less
  fragmented file allocations in the future.

  Before you can defragment a file domain, all filesets	in the file domain
  must be mounted. If you try to defragment an active file domain that
  includes unmounted filesets, the system displays an error message indicat-
  ing that a fileset is	unmounted.

  To determine the amount of file fragmentation	in a file domain, run the
  defragment command with the -v and -n	options. This provides the fragmenta-
  tion information without starting the	defragmentation	process. Run defrag-
  ment with the	-v and -n options again	to see the improvement.

  Before running the defragment	utility, delete	any files in the domain	that
  you do not need. This	gives the defragment utility more free space to	use,
  which	produces better	results.  Deleting files afterwards creates only more
  free-space fragments.	It is also a good idea to run the balance utility on
  the domain before you	run the	defragment utility in order to balance domain
  free space before defragmenting the domain files.

  To monitor the improvement made to the file domain by	the defragment util-
  ity, use the verbose mode option, -v,	which displays the following informa-
  tion:

    +  Extents

       The number of extents in	the specified domain. (Contiguous extents in
       sparse files are	counted	as one extent after defragmentation, when in
       fact there are several contiguous file extents.)

    +  Files w/	extents

       The number of files that	have extents. (Note that files do not have
       extents if the files are	less than 7 Kilobytes.)

    +  Avg exts	per file w/ exts

       The average number of extents for each file that	has one	or more
       extents.

    +  Aggregate I/O perf

       The efficiency of the entire file domain. An increase in	value indi-
       cates improvement.

    +  Free space fragments

       The number of free-space	fragments in the domain.

RESTRICTIONS

  The defragment utility requires a minimum of 1 percent of the	total space,
  or 5 megabytes per volume (whichever is less)	to defragment that volume.

  You cannot run the defragment	utility	while the addvol, balance, defrag-
  ment,	rmfset,	or rmvol utility is running on the same	file domain.

  You must be the root user to use this	utility.






EXAMPLES

  The following	example	defragments the	file domain called accounts_dmn. A
  flexible time	limit of 15 minutes is imposed and verbose mode	is requested
  to display the fragmentation data:

       # defragment -v -t 15 accounts_dmn

       defragment: defragmenting domain	'accounts_dmn'

       Pass 1; Clearing

	 Volume	1: area	at block    11680 (  103072 blocks): 81% full
	 Domain	data as	of the start of	this pass:
	   Extents:		     10432
	   Files w/extents:	      4305
	   Avg exts per	file w/exts:  2.42
	   Aggregate I/O perf:	       52%
	   Free	space fragments:      2743
			    <&lt;100K    <&lt;1M    <&lt;10M    >&gt;10M
	     Free space:     38%      0%      0%     62%
	     Fragments:	    2742       0       0       1

       Filling
       .
       .
       .
       Pass 13;	Clearing
	 Volume	1: area	at block   559744 (   62736 blocks):  0% full
	 Volume	2: area	at block    76640 (   24624 blocks): 18% full
	 Domain	data as	of the start of	this pass:
	   Extents:		      4306
	   Files w/extents:	      4305
	   Avg exts per	file w/exts:  1.00
	   Aggregate I/O perf:	      100%
	   Free	space fragments:	23
			    <&lt;100K    <&lt;1M    <&lt;10M    >&gt;10M
	     Free space:      0%      9%     27%     64%
	     Fragments:	       6      10       5       2

       Filling

	 Current domain	data:
	   Extents:		      4305
	   Files w/extents:	      4305
	   Avg exts per	file w/exts:  1.00
	   Aggregate I/O perf:	      100%
	   Free	space fragments:	17
			    <&lt;100K    <&lt;1M    <&lt;10M    >&gt;10M
	     Free space:      0%      6%     29%     65%
	     Fragments:	       3       8       4       2

       defragment: defragmented	domain 'accounts_dmn'

  The information displayed before each	pass and at the	conclusion of the
  defragmentation process shows	the improvement	made to	the file domain	by
  the defragment utility.



SEE ALSO

  Commands: addvol(8), balance(8), rmvol(8)