• Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint
Share this Page URL
Help

tunefs

tunefs

tunefs Tunes up an existing file system.
tunefs [-A] [-a <maxcontig>] [-d <rotdelay>] [-e <maxbpg>] [-m <min-
									free>] [-o <optimize_preference>] [<special> | <filesystem>]

tunefs is designed to change the dynamic parameters of a file system that affect the layout policies. The parameters which are to be changed are indicated by the flags given here:
-A The file system has several backups of the superblock. Specifying this option will cause all backups to be modified as well as the primary super-block. This is potentially dangerous—use it with caution.
-a <maxcontig> Specifies the maximum number of contiguous blocks that will be laid out before forcing a rotational delay (see -d). The default value is 1 because 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> 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> 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 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 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, but 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 <optimize-preference> The file system can either try to minimize the time spent allocating blocks, or it can attempt to minimize the space fragmentation on the disk. If the value of minfree (see above) is less than 10%, 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.
-p This option shows a summary of what the current tuneable settings are on the selected file system. More detailed information can be obtained in the dumpfs(8) manual page.



PREVIEW

                                                                          

Not a subscriber?

Start A Free Trial


  
  • Creative Edge
  • Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint