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



NAME    [Toc]    [Back]

       tunefs - Tunes an existing UFS file system

SYNOPSIS    [Toc]    [Back]

       /usr/sbin/tunefs  [-a maxcontig] [-d rotdelay] [-e maxbpg]
       [-m minfree] [-o optimization_preference] file_system

OPTIONS    [Toc]    [Back]

       Specifies the maximum number  of  contiguous  blocks  that
       will  be  laid  out before forcing a rotational delay (see
       the -d option).  The default value is  8.  Device  drivers
       that can chain several buffers together in a single transfer
 should set this to the maximum chain  length.   Specifies
  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.
       Indicates 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,
 you set this value to  about  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
       frequently 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.  Specifies the percentage of space
       held back  from  normal  users;  the  minimum  free  space
       threshold.  The  default value used is 10%. This value can
       be set to zero; however,  up  to  a  factor  of  three  in
       throughput will be lost over the performance obtained at a
       10% threshold. Note that 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.  Specifies whether the file system
       should try to minimize the time  spent  allocating  blocks
       (-o  time)  or  try to minimize the space fragmentation on
       the disk (-o space).

              If the value of  minfree  (see  the  previous  list
              item) is less than 10%, then the file system should
              optimize for space to avoid  running  out  of  full
              sized blocks. For values of minfree greater than or
              equal to 10%, fragmentation is  unlikely  to  be  a
              problem,  and  the file system can be optimized for

OPERANDS    [Toc]    [Back]

       Specifies the UFS file system that is being tuned.

DESCRIPTION    [Toc]    [Back]

       The tunefs command changes the dynamic parameters of a UFS
       file  system  that affect the layout policies. The parameters
 to be changed are indicated by the options specified.

       You should unmount a file system before running the tunefs
       program. The tunefs program does allow you to enter parameters
 for a mounted and active file system.  However, your
       changes will not take effect  until  the  file  system  is
       unmounted  and mounted again (or until after the system is
       rebooted). If you use tunefs to tune the root file  system
       (assuming  root  is  a  UFS  file system), you must always
       reboot the system  in  order  for  your  changes  to  take

       For  larger-capacity devices, set minfree to five percent.

       The rotdelay value is useful for disks that  do  not  have
       read-ahead  cache, such as the RA-series disks.  For disks
       that have read-ahead cache, set rotdelay to zero.

       After you specify an  optimization  preference,  it  comes
       into  play  only under the following conditions: A file is
       growing It is not possible to extend a fragment There is a
       choice between allocating an exact-sized fragment or allocating
 a full block and freeing the unused portion of  the

       After  you  specify an optimization preference, the system
       first tries the specified preference when it  reaches  the
       minimum  reserved space specified by the minfree value. If
       you specified -o space, the system tries  space  optimization,
  but  switches to time optimization if the file continues
 to grow and fragmentation is less than half of  the
       minimum  free reserve. If you specifed -o time, the system
       tries time optimization, but switches to  space  optimization
 if the file growth causes disk fragmentation to reach
       within two percent of the minimum free reserve.

       You must be the root user to use this command.

FILES    [Toc]    [Back]

       Specifies the command path.

SEE ALSO    [Toc]    [Back]

       Commands: newfs(8)

[ Back ]
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