tunefs(8)						      System Manager's Manual							 tunefs(8)

Name
       tunefs - tune up an existing file system

Syntax
       /etc/tunefs [ options ]

Description
       The command is designed to change the dynamic parameters of a file system which affect the layout policies.  The parameters which are to be
       changed are indicated by the options listed in the following section.

Options
       -a maxcontig
		 This specifies 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 sev-
		 eral buffers together in a single transfer should set this to the maximum chain length.

       -d rotdelay
		 This 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.

       -e maxbpg This  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 this value is set to about one quarter of the total blocks in a  cylin-
		 der  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.

       -m minfree
		 This value 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.

       -c	 Clean	byte  timeout  factor.	The metrics used to determine if a clean byte associated with a file system should be invalidated,
		 decrement a timeout factor when crossed.  When the timeout factor reaches zero, the clean byte is invalidated and will  automati-
		 cally	check  the  file  system.  The timeout factor can be increased to a value between 0 and 255. A value of zero will cause to
		 check the file system on every reboot.

Restrictions
       This program should work on mounted and active file systems.  Because the super-block is not kept in the buffer	cache,	the  program  will
       only take effect if it is run on dismounted file systems.  If run on the root file system, the system must be rebooted.

See Also
       fs(5), fsck(8), mkfs(8), newfs(8)
       ``A Fast File System for UNIX,'' ULTRIX Supplementary Documents, Volume 3: System Manager

																	 tunefs(8)