Manual Pages for UNIX Operating System command usage for man tunefs

System Administration Commands                         tunefs(1M)



NAME
     tunefs - tune an existing UFS file system

SYNOPSIS
     tunefs [-a maxcontig] [-d rotdelay] [-e maxbpg]
          [-m minfree] [-o space | time] special | filesystem


DESCRIPTION
     tunefs is designed to change the  dynamic  parameters  of  a
     file  system  that  affect  the  layout policies. When using
     tunefs with filesystem, filesystem must be  in  /etc/vfstab.
     The  parameters  that  can  be  changed are indicated by the
     options given below.

OPTIONS
     The following options are supported:

     -a maxcontig         The maximum number of  logical  blocks,
                          belonging  to  one  file, that is allo-
                          cated contiguously. The default is cal-
                          culated as follows:

                            maxcontig = disk drive maximum transfer size / disk block size


                          If the disk  drive's  maximum  transfer
                          size  cannot be determined, the default
                          value for maxcontig is calculated  from
                          kernel parameters as follows:

                          If maxphys is less than ufs_maxmaxphys,
                          which is 1 Mbyte, then maxcontig is set
                          to maxphys. Otherwise, maxcontig is set
                          to ufs_maxmaxphys.

                          You can set maxcontig to  any  positive
                          integer value.

                          The actual value will be the lesser  of
                          what  has  been  specified and what the
                          hardware supports.


     -d rotdelay          This parameter is obsolete  as  of  the
                          Solaris 10 release. The value is always
                          set  to  0,  regardless  of  the  input
                          value.


     -e maxbpg            Indicates the maximum  number  of  con-
                          tiguous  logical blocks any single file



SunOS 5.11           Last change: 5 Dec 2003                    1






System Administration Commands                         tunefs(1M)



                          can  allocate  from  a  cylinder  group
                          before it is forced to begin allocating
                          blocks  from  another  cylinder  group.
                          Typically this value is set to approxi-
                          mately one quarter of  the  total  con-
                          tiguous  logical  blocks  in a cylinder
                          group. The intent  is  to  prevent  any
                          single  file  from  using  up  all  the
                          blocks in a single cylinder group, thus
                          degrading  access  times  for all files
                          subsequently allocated in that cylinder
                          group.

                          The effect of this limit  is  to  cause
                          big  files  to  do long seeks more fre-
                          quently than if they  were  allowed  to
                          allocate  all  the blocks in a cylinder
                          group  before  seeking  elsewhere.  For
                          file  systems  with  exclusively  large
                          files, this  parameter  should  be  set
                          higher.


     -m minfree           Specifies the minimum free space thres-
                          hold,  or  the percentage of space held
                          back from normal users. This value  can
                          be set to 0. However, up to a factor of
                          three in throughput will be  lost  over
                          the   performance  obtained  at  a  10%
                          threshold. Note: If the value is raised
                          above  the  current  usage level, users
                          will be unable to allocate files  until
                          enough  files  have been deleted to get
                          under the higher threshold.


     -o space|time        The   file   system   can   either   be
                          instructed  to try to minimize the time
                          spent allocating blocks, or to  try  to
                          minimize the space fragmentation on the
                          disk. The default is time.

                          Generally, you should optimize for time
                          unless  the  file  system  is  over 90%
                          full.


USAGE
     See largefile(5) for the  description  of  the  behavior  of
     tunefs  when  encountering  files greater than or equal to 2
     Gbyte ( 2^31 bytes).




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System Administration Commands                         tunefs(1M)



ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Availability                | SUNWcs                      |
    |_____________________________|_____________________________|


SEE ALSO
     mkfs_ufs(1M), newfs(1M), attributes(5), largefile(5)








































SunOS 5.11           Last change: 5 Dec 2003                    3