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SunOS man pages : tunefs (1)

Maintenance Commands                                   tunefs(1M)


tunefs - tune up an existing file system


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


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.


-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


See largefile(5) for the description of the behavior of tunefs when encountering files greater than or equal to 2 Gbyte ( 2**31 bytes).


See attributes(5) for descriptions of the following attri- butes: ____________________________________________________________ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | |_____________________________|_____________________________| | Availability | SUNWcsu | |_____________________________|_____________________________|


mkfs(1M), fork(2), terminfo(4), attributes(5), largefile(5) SunOS 5.8 Last change: 18 Feb 1999 2