tune up an existing file system
tunefs [-AN] [-a maxcontig] [-d rotdelay]
[-e maxbpg] [-m minfree] [-o optimize_preference]
[-t trackskew] [special | filesys]
Changes the dynamic parameters of a file system which affect the layout policies.
cannot be run on an active file system, it must be downgraded to read-only or unmounted.
|displays settable options (after any changes from the tuning options)
| ommiting |
| update only standard superblock
|Alternate superblocks are also updated. |
If a run of fsck uses an alternate superblock, which has not been updated, parameters will be those previosly written to that alternate.
| percentage of space held back from normal users(i.e.non root); the minimum free space threshold.|
Default 10%. If set to zero, up to a factor of three
in throughput will be lost over the performance obtained at a 10% threshold.
If space is allocated above the threshold, users will be unable to allocate files until enough files
have been deleted to get under the higher threshold.
This reserves space for root in the event of a rogue process or syslog logs (local or remote) attempting to consume all the space on the file system.
| expected time (in ms ) to service a transfer completion interrupt
and initiate a new transfer on the same disk. Used to decide how much rotational spacing
to place between successive blocks in a file.
| maximum number of contiguous blocks before forcing a rotational delay .|
default is one
Device drivers that can chain several buffers together in a
single transfer should set this to the maximum chain length.
| maximum number of blocks out of a cylinder group before being forced to change to another group. |
Use one quarter of the blocks in a cylinder group.
preventing any 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.
| expected average file size.
|expected number of files per directory.
space | time
| Optimize for minimum space fragmentation or time spent allocating blocks. |
Optimization for space has high overhead for file writes.
minFree is less than 10%, then optimize for space to avoid running out of full sized blocks.
minFree greater than 10%, optimized for time.
| the skew, in sectors, from one track to the next in a cylinder. |
Default zero, meaining that each track in a cylinder begins at the same rotational position.
sudo umount /dev/disk0s14
sudo tunefs -N /dev/disk0s14
tunefs: current settings
maximum contiguous block count 32
rotational delay between contiguous blocks 0ms
maximum blocks per file in a cylinder group 1024
minimum percentage of free space 5%
optimization preference: time
track skew 0 sectors
expected average file size 16384
expexted number of files per directory 64
tunefs: no changes made
At least one of the above flags is required.
SEE tune2fs,fs, dumpfs, fsck, newfs
You can tune a file system, but you can't tune a fish.
4.2 Berkeley Distribution May 3, 1995 4.2 Berkeley Distribution
Usage: tunefs [-AN] tuneup-options special-device
where tuneup-options are:
-d rotational delay between contiguous blocks
-a maximum contiguous blocks
-e maximum blocks per file in a cylinder group
-m minimum percentage of free space
-o optimization preference (`space' or `time')
-t track skew in sectors
-f expected average file size
-s expected number of files per directory