tunefs(8) CLIX tunefs(8)
NAME
tunefs - Tunes an existing Fast File System (FFS)
SYNOPSIS
/etc/tunefs flag ... {special|filesys}
FLAGS
-a maxcontig Specifies the maximum number of contiguous blocks allocated
before forcing a rotational delay. (See -d below.) The
default value is 1, since most device drivers require an
interrupt for each disk transfer. Device drivers that can
chain several buffers together in a single transfer should
set this parameter to the maximum chain length.
-d rotdelay Specifies the expected time (in milliseconds) to service a
transfer completion interrupt and initiates a new transfer
on the same disk. This value is used to decide how much
rotational spacing to place between successive blocks in a
file.
-e maxbpg Specifies the maximum number of blocks any single file can
allocate from a cylinder group before it is forced to
allocate blocks from another cylinder group. This value is
typically set to approximately one quarter of the total
blocks in a cylinder group. The intent is to prevent any
single file from using all the blocks in a single cylinder
group, thus degrading access times for all files
subsequently allocated in that cylinder group. This limit
causes large files to perform long seeks more frequently
than if they were allowed to allocate all 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 is 10%. This value can be set to 0. However,
throughput can decrease by a factor of 3 over that 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 mode Sets optimization mode, specified by mode, which may be
either space or time. The file system either attempts to
minimize the time spent allocating blocks or to minimize
the space fragmentation on the disk. If the value of
minfree (see above) is less than 10%, the file system
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tunefs(8) CLIX tunefs(8)
optimizes 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 a problem, and the
file system can be optimized for time.
DESCRIPTION
The tunefs command changes the dynamic parameters of the Fast File System
(FFS) represented by the special device file or the named filesys. These
parameters affect the layout policies. The parameters to be changed are
indicated by the flags (listed and defined in the FLAGS section). At
least one flag must appear on the command line.
EXAMPLES
1. This example sets the optimization mode for the file system mounted at
/mnt to time.
tunefs -o time /mnt
2. This example sets the minimum free space to 5% for the /usr file
system.
tunefs -m 5 /dev/dsk/s0u0p7.3
CAUTIONS
The tunefs command should work on mounted and active file systems.
Because the superblock is not kept in the buffer cache, the changes will
take effect only if the program is run on unmounted file systems. To
change the root file system, the system must be rebooted after the file
system is tuned.
DIAGNOSTICS
The following message appears if the named file was not a mount point or a
device file.
[device] not a block or character special device
EXIT VALUES
The following is a list of the valid exit values for the tunefs command.
0 Command completed successfully.
1 System call error.
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tunefs(8) CLIX tunefs(8)
2 Usage error.
RELATED INFORMATION
Commands: newfs(8), ffsmkfs(8)
Files: fs(4)
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