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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
utility 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
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
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
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
Commands: addvol(8), balance(8), rmvol(8), vfast(8)
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Index for
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