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vfast(8)
NAME
vfast - Runs the vfast utility in the background to reduce file
fragmentation, and to balance volume free space and I/O load.
SYNOPSIS
/sbin/advfs/vfast [activate | deactivate | suspend |status] domain
/sbin/advfs/vfast [-l | -L {-extents | -hotfiles }] domain
/sbin/advfs/vfast -o option_list domain
OPTIONS
The vfast utility has control, display, processing and configuration
options.
The following are control options:
activate
Activates vfast operation on the domain.
deactivate
Deactivates all vfast operation on the domain and stops gathering any
internal statistics. This is the default.
status
Displays the current vfast configuration, operational statistics, and
processing options for the domain.
suspend
Temporarily disables all vfast option processing on the domain but
continues to gather internal statistics.
The following are display options:
-l Displays extents and hotfiles (most actively paging files) for a volume
and domain.
extents
Displays the files currently queued for defragmentation and volume
free space balancing.
hotfiles
Displays the most actively paging files and the volumes on which
they reside.
-L Displays extent and hotfile (most actively paging files) summary
statistics for a domain.
extents
Displays fragmentation summaries by volume.
hotfiles
Displays a distribution summary by volume and domain of the most
actively paging files.
-o option_list
Allows you to change one or more processing options or processing
configurations by specifying a comma-separated list.
The following are processing options for the -o option:
balance=
Equalizes free space across all volumes in a domain by moving
fragmented files between volumes.
enable
Enables free space balancing on the domain. The defragment= option
must be enabled.
disable
Disables free space balancing on the domain. This is the default.
defragment=
Consolidates file extents on the domain.
enable
Enables file defragmentation on the domain.
disable
Disables file defragmentation on the domain. This is the default.
topIObalance=
Distributes files with high I/O among volumes to improve I/O
throughput.
enable
Enables volume I/O load balancing on the domain.
disable
Does not perform volume I/O load balancing. This is the default.
The following are configuration options for the -o option:
direct_io=
Manages vfast effects on files that are currently enabled for direct
I/O.
enable
Allows vfast to defragment files that are using direct I/O. This is
the default.
disable
Prevents vfast from defragmenting files that are using direct I/O.
ss_steady_state=
Specifies the number of hours from the first writable fileset mount to
the start of top I/O balancing.
percent_ios_when_busy=
Limits the share of system I/O that -vfast uses to a maximum of the
percent specified. However, most vfast processing occurs when devices
have no other system I/O. The default is 1 percent. The high limit for
percent_ios_when_busy= is 50 percent.
OPERANDS
domain
Specifies the domain name.
DESCRIPTION
The vfast utility runs at the operating system level with low overhead,
continuously defragmenting and balancing files, consolidating free space
and distributing the file I/O over the volumes of a domain. It only
processes files that are actively being opened and closed. The utility
automatically runs during periods of low system demand so that system
administrators do not have to take a system off line.
The vfast utility balances the available free space over volumes to
maximize file-creation performance. It defragments all active files
including the frag file and the root tag file. The system administrator
does not need to perform balance and defragment maintenance tasks. The
utility also uses file I/O statistics gathered by the AdvFS kernel to
distribute files with high I/O to different volumes in the domain
The vfast utility takes into account reserved file access, but it does not
move any of the reserved files.
Files or filesets with direct I/O enabled might be moved when consolidating
free space.
The features of vfast that are in effect and the system activity that
occurs from running the command are displayed by the vfast -status option
for the specified domain:
· Defragment
Consolidation of free space.
· Balance
Distribution of files to different volumes.
· TopIObalance
Continuous distribution of files with high I/O to different volumes.
· Direct I/O File Processing
Processing files that have direct I/O enabled.
· Percent IOs Allocated to vfast when System Busy
Controls the utility's access to system resources.
· Default Hours until Steady State
Time that must elapse while the system collects statistics before I/O
balancing operations start.
· Total Files Defragmented
The number of files that have been moved to more contiguous locations
on disk.
· Total Pages Moved for Defragment
The number of pages that were moved to more contiguous locations on
disk.
· Total Extents Combined for Defragment
The number of file extents that were consolidated.
· Total Pages Moved for Balance
The number of pages that were moved to equalize free space on the
volumes of the domain.
· Total Files Moved for Volume IO Balance
The number of files that were moved to equalize I/O load on the
volumes of the domain.
· Total Pages Moved for Volume Free Space Consolidation
The number of pages that were moved to create contiguous space on the
volumes of the domain.
The vfast -l command displays the following information about the specified
domain by volume:
· Extent Count
Number of extents per file. Files that are less than 8 kilobytes have
no extents.
· Fileset / File
Name of filesets and files with extents.
The vfast -L command displays the information of the vfast -l command and
also:
· Average Extents per File with Extents
The average number of extents for each file that has one or more
extents.
· Free Space Fragments
The number of free space fragments.
· Free Space
The percentage of fragments by size.
· Fragments
The number of fragments by size.
RESTRICTIONS
Do not enable topIObalance= if your domain has multiple volumes created on
the same disk. The utility cannot effectively distribute the I/O load
because there is only one I/O bus.
Do not enable topIObalance= if your domain is composed of LSM striped
volumes or LSM volumes that are a concatenation of partitions from multiple
storage devices or partitions. Also disable this option when using RAID
devices with striping enabled. The utility cannot effectively distribute
the I/O load.
If vfast is activated and defragment=, balance=, or topIObalance= are
enabled on a domain, then the standard AdvFS balance and defragment
utilities are not available.
If direct_io= is enabled, files enabled with direct IO are not evaluated
for top I/O balance because I/O on these files bypasses vfast statistics
collection. However, they can still be moved by vfast when free space is
consolidated to make room for files being defragmented.
The vfast -o balance= operation is not enabled unless defragment= is also
enabled.
If you reboot or unmount all filesets in a given domain, current file I/O
histories are lost. It is possible to temporarily suspend vfast processing
and not lose the internal statistics and files queued for defragmenting by
changing vfast to suspend mode. The standard AdvFS defragment and balance
utilities can be run while vfast is in suspend or deactivate mode.
If a system node is a cluster member, some files may not be processed
initially because cluster file system (CFS) caches files and processing
cannot occur until the cache is flushed.
EXAMPLES
The following example changes the processing options:
# vfast -o defragment=enable,balance=enable,topIObalance=enable q_domain
# vfast status q_domain
vfast is currently running
vfast is activated on q_domain
vfast defragment: enabled
vfast balance: enabled
vfast top IO balance: enabled
Options:
Direct IO File Processing: enabled
Percent IOs Allocated to vfast When System Busy: 1%
Default Hours Until Steady State: 24; Hours remaining: 0
Total Files Defragmented: 44208
Total Pages Moved for Defragment: 5873696
Total Extents Combined for Defragment: 12212
Total Pages Moved for Balance: 248266
Total Files Moved for Volume IO Balance: 1
Total Pages Moved for Volume Free Space Consolidation: 914
The following example summarizes the extents by volume for the domain
x_domain:
# vfast -l extents x_domain
x_domain: Volume 1
extent
count fileset/file
No extents
x_domain: Volume 2
extent
count fileset/file
5 foo: /qfoo/sub1/sub2/lockf
32 foo: /qfoo/sub1/sub2/tmp.vmunix.cp0
x_domain: Volume 3
extent
count fileset/file
5 foo: /qfoo1/sub1/sub2/nvbmtpg.BSR_DMN_SS_ATTR
2 foo: /qfoo1/sub1/sub2/mount
10 foo: /qfoo1/sub1/sub2/quota.user
3 foo: /qfoo1/sub1/sub2/vfast
144 foo: /qfoo1/sub1/sub2/tmp.vmunix.cp1
140 foo: /qfoo1/sub1/sub2/tmp.vmunix.cp2
The following example displays extents for the files in the domain
usr_domain:
# vfast -L extents usr_domain
usr_domain
Extents: 15745
Files w/extents: 9103
Avg exts per file w/exts: 1.73
Free space fragments: 2320
<100K <1M <10M> 10M
Free space: 2% 1% 2% 95%
Fragments: 2175 115 13 17
FILES
/sbin/advfs/vfast
SEE ALSO
Commands: defragment(8) , balance(8)
Files: advfs(4)
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Index for
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Alphabetical
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