Content-type: text/html Man page of defragment

defragment

Section: Maintenance Commands (8)
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NAME

defragment - Makes the files in a file domain more contiguous  

SYNOPSIS

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


 

OPTIONS

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

OPERANDS

Specifies the name of the file domain.
 

DESCRIPTION

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 before using the defragment utility, issue the defragment command with the -v and -n options. This provides the fragmentation information without starting the defragment utility.

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 more free-space fragments.

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 so small that they are kept with the metadata.) 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

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

The defragment utility does not defragment striped files.

You cannot run the defragment utility while the addvol, balance, defragment, 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
                     <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% 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
                     <100K    <1M    <10M    >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
                     <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

addvol(8), balance(8), rmvol(8)


 

Index

NAME
SYNOPSIS
OPTIONS
OPERANDS
DESCRIPTION
RESTRICTIONS
EXAMPLES
SEE ALSO

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Time: 02:40:28 GMT, October 02, 2010