TUNEFS(1M)TUNEFS(1M)NAMEtunefs - tune an existing UFS file system
SYNOPSIStunefs [-a maxcontig] [-d rotdelay] [-e maxbpg]
[-m minfree] [-o space | time] special | filesystem
DESCRIPTIONtunefs 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. Other‐
wise, 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.
-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This parameter is obsolete as of the Solaris 10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 cylin‐
der 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. However, up to a fac‐
tor 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 fragmentation 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).
SEE ALSOmkfs_ufs(1M), newfs(1M), attributes(5), largefile(5)BUGS
You can tune a file system, but you can't tune a fish.
Sep 19, 2013 TUNEFS(1M)
