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tunefs(8) [bsd man page]

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

NAME
tunefs - tune up an existing file system SYNOPSIS
tunefs tuneup-options special|filesys DESCRIPTION
Tunefs 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 flags given below: -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 several buf- fers 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 allo- cating blocks from another cylinder group. Typically this value is set 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. -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. -o optimization preference The file system can either try to minimize the time spent allocating blocks, or it can attempt minimize the space fragmentation on the disk. If the value of minfree (see above) 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 problematical, and the file system can be optimized for time. SEE ALSO
fs(5), newfs(8), mkfs(8) M. McKusick, W. Joy, S. Leffler, R. Fabry, ``A Fast File System for UNIX'', ACM Transactions on Computer Systems 2, 3. pp 181-197, August 1984. (reprinted in the System Manager's Manual, SMM:14) BUGS
This program should work on mounted and active file systems. Because the super-block is not kept in the buffer cache, the changes will only take effect if the program is run on dismounted file systems. To change the root file system, the system must be rebooted after the file system is tuned. tunefs is not currently implemented in 2.11BSD. You can tune a file system, but you can't tune a fish. 4.2 Berkeley Distribution November 17, 1996 TUNEFS(8)

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tunefs(1M)						  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 allocated contiguously. The default is calculated 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_maxmax- phys. 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 contiguous logical blocks any single file can allocate from 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 contiguous 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 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 Specifies the minimum free space threshold, or the percentage of space held back from normal users. This value can be set to 0. How- ever, 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 fragmen- tation 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). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ SEE ALSO
mkfs_ufs(1M), newfs(1M), attributes(5), largefile(5) SunOS 5.10 5 Dec 2003 tunefs(1M)

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