tunefs - tune an existing UFS 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 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.
The following options are supported:
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 calcu-
lated 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_maxmaxphys.
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.
This parameter is obsolete. The value is always set to
0, regardless of the input value.
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 contigu-
ous 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.
Specifies the minimum free space threshold, or the
percentage of space held back from normal users. This
value 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.
The file system can either be instructed to try to
minimize the time spent allocating blocks, or to try
to minimize the space fragmentation on the disk. The
default is time.
Generally, you should optimize for time unless the
file system is over 90% full.
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-
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Availability | SUNWcsu |
mkfs_ufs(1M), newfs(1M), attributes(5), largefile(5)
Man(1) output converted with