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  man pages->Tru64 Unix man pages -> defragment (8)              



NAME    [Toc]    [Back]

       defragment  -  Makes  the files in a file domain more contiguous

SYNOPSIS    [Toc]    [Back]

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

OPTIONS    [Toc]    [Back]

       Ignores errors and continues, if possible. Errors that are
       ignored are usually related to a specific file.  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.  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.  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.   Specifies  an exact time interval (in minutes)
       for the defragment utility to run. When the specified time
       has  elapsed, the defragmentation procedure stops, even if
       it is performing an operation.  Displays statistics on the
       amount of fragmentation in the file domain and information
       on the progress of the defragment procedure.  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

OPERANDS    [Toc]    [Back]

       Specifies the name of the file domain.

DESCRIPTION    [Toc]    [Back]

       When a file consists of many discontiguous  file  extents,
       the  file  is  fragmented  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  indicating  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 fragmentation information without
 starting the defragmentation process.  Run  defragment
       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 utility, use the verbose mode option, -v, which
       displays the following information: 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  indicates  improvement.   Free
              space fragments

              The number of free-space fragments in the domain.

RESTRICTIONS    [Toc]    [Back]

       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 must be the root user to use this utility.

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

       If the vfast utility is activated and defragment, balance,
       or topIObalance are enabled on that domain, then the standard
 AdvFS balance and defragment utilities are not available.

       Running the defragment -nv command  on  a  domain  with  a
       large  amount of metadata can cause it to fail. To prevent
       this from happening, double the size of per_proc_data_size
       with  the  sysconfig command or  specify the doubled value
       in the /etc/sysconfigtab file.

EXAMPLES    [Toc]    [Back]

       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%
         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
                            <100K    <1M    <10M    >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%
         Volume  2: area at block    76640 (   24624 blocks): 18%
         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
                            <100K    <1M    <10M    >10M
             Free space:      0%      9%     27%     64%
             Fragments:        6      10       5       2


         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
                            <100K    <1M    <10M    >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    [Toc]    [Back]

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

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