tunefs_sfs -- tune up an existing filesystem


tunefs [-a maxcontig] [-d rotdelay] [-e maxbpg]
[-o [s | space | t | time]] special | filesystem


tunefs is designed to change the dynamic parameters of a filesystem which affect the layout policies. The filesystem must be unmounted before using tunefs. The parameters which are to be changed are indicated by the options given below:

The options are:

-a maxcontig
Specify the maximum number of contiguous blocks that will be laid out before forcing a rotational delay (see -d below). The default value is one, since most device drivers require an interrupt per disk transfer. Device drivers that can chain several buffers together in a single transfer should set this to the maximum chain length.

-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 approximately 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 filesystems with exclusively large files, this parameter should be set higher.

-o [s | space | t | time]
Change optimization strategy for the filesystem. s and space are interchangeable, and t and time are interchangeable.

s or space
Conserve space.

t or time
Organize file layout to minimize access time.

Generally one should optimize for time unless the filesystem is over 90% full.


fork(2), fs_sfs(4), generic mkfs(1M), terminfo(4)


The tunable minfree is not supported on sfs file systems.
© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 25 April 2004