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



NAME    [Toc]    [Back]

       vfast - Runs the vfast utility in the background to reduce
       file fragmentation, and to balance volume free  space  and
       I/O load.

SYNOPSIS    [Toc]    [Back]

       /sbin/advfs/vfast  [activate  | deactivate | suspend |status]

       /sbin/advfs/vfast [-l | -L {-extents | -hotfiles }] domain

       /sbin/advfs/vfast -o option_list domain

OPTIONS    [Toc]    [Back]

       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 gathering  any  internal  statistics.
       This  is the default.  Displays the current vfast configuration,
 operational statistics, and processing options for
       the  domain.   Temporarily  disables all vfast option processing
 on the domain but  continues  to  gather  internal
       statistics.   Displays 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
       hotfile (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 configurations by
       specifying  a  comma-separated list.  Equalizes free space
       across all volumes in a domain by moving fragmented  files
       between  volumes.   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  balancing  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  defragmenting  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 balancing.
       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    [Toc]    [Back]

       Specifies the domain name.

DESCRIPTION    [Toc]    [Back]

       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    [Toc]    [Back]

       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    [Toc]    [Back]

       The following example changes the  processing  options:  #
       vfast     -o    defragment=enable,balance=enable,topIObalance=enable

       # 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:

       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

          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    [Toc]    [Back]


SEE ALSO    [Toc]    [Back]

       Commands: defragment(8) , balance(8)

       Files: advfs(4)

[ Back ]
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