Maintenance Commands                                   tunefs(1M)

NAME
     tunefs - tune up an existing 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  which  affect  the layout policies. When using
     tunefs with  filesystem, filesystem must be in  /etc/vfstab.
     The  parameters which are to be changed are indicated by the
     options given below.

     Generally one should optimize for time unless the file  sys-
     tem is over 90% full.

OPTIONS
     -a maxcontig
           Specify the maximum number of contiguous  blocks  that
           will  be  laid  out  before forcing a rotational delay
           (see -d). The default value  is  determined  from  the
           disk  drive's  maximum transfer rate. The maximum max-
           config that UFS supports is 10486576.

     -d rotdelay
           Specify the expected time (in milliseconds) to service
           a  transfer  completion  interrupt  and initiate a new
           transfer on the same disk. It is used  to  decide  how
           much  rotational  spacing  to place between successive
           blocks in a file.

     -e maxbpg
           Indicate the maximum number of blocks any single  file
           can  allocate  out  of  a  cylinder group before it is
           forced  to  begin  allocating  blocks   from   another
           cylinder group. Typically this value is set to approx-
           imately one quarter of the total 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
           Specify the percentage of space held back from  normal
           users;  the  minimum  free space threshold. This value

SunOS 5.8           Last change: 18 Feb 1999                    1

Maintenance Commands                                   tunefs(1M)

           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]
           Change optimization strategy for the file system.

           space: conserve space

           time: attempt to  organize  file  layout  to  minimize
           access time

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).

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

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Availability                | SUNWcsu                     |
    |_____________________________|_____________________________|

SEE ALSO
     mkfs(1M), fork(2), terminfo(4), attributes(5), largefile(5)

SunOS 5.8           Last change: 18 Feb 1999                    2