tunefs(1M) manual page
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tunefs - tune up an existing file system
tunefs [ -a maxcontig
] [ -d rotdelay ] [ -e maxbpg ] [ -m minfree ] [ -o [ space | time ]] special | filesystem
SUNWcsu
tunefs is designed to change the dynamic
parameters of a file system which affect the layout policies. The file system
must be unmounted before using tunefs. 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 system 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 below). The default value is 1, since 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
- 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 approximately 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
- Specify 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 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
mkfs(1M)
,
fork(2)
, terminfo(4)
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