vfast(8)vfast(8)NAMEvfast - Runs the vfast utility in the background to reduce file frag‐
mentation, 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: Activates vfast operation on the
domain. Deactivates all vfast operation on the domain and stops gath‐
ering any internal statistics. This is the default. Displays the cur‐
rent vfast configuration, operational statistics, and processing
options for the domain. Temporarily disables all vfast option process‐
ing on the domain but continues to gather internal statistics. Dis‐
plays extents and hotfiles (most actively paging files) for a volume
and domain. Displays the files currently queued for defragmentation
and volume free space balancing. Displays the most actively paging
files and the volumes on which they reside. Displays extent and hot‐
file (most actively paging files) summary statistics for a domain.
Displays fragmentation summaries by volume. Displays a distribution
summary by volume and domain of the most actively paging files. Allows
you to change one or more processing options or processing configura‐
tions by specifying a comma-separated list. Equalizes free space
across all volumes in a domain by moving fragmented files between vol‐
umes. Enables free space balancing on the domain. The defragment=
option must be enabled. Disables free space balancing on the domain.
This is the default. Consolidates file extents on the domain. Enables
file defragmentation on the domain. Disables file defragmentation on
the domain. This is the default. Distributes files with high I/O
among volumes to improve I/O throughput. Enables volume I/O load bal‐
ancing on the domain. Does not perform volume I/O load balancing.
This is the default. Manages vfast effects on files that are currently
enabled for direct I/O. Allows vfast to defragment files that are
using direct I/O. This is the default. Prevents vfast from defragment‐
ing files that are using direct I/O. Specifies the number of hours
from the first writable fileset mount to the start of top I/O balanc‐
ing. 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
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 consoli‐
dating 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 vol‐
umes. 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 Bal‐
ance
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 spec‐
ified 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 mul‐
tiple storage devices or partitions. Also disable this option when
using RAID devices with striping enabled. The utility cannot effec‐
tively 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 evalu‐
ated for top I/O balance because I/O on these files bypasses vfast sta‐
tistics 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)vfast(8)
