fstrim
discard unused blocks on a mounted filesystem
see also :
mount
Synopsis
fstrim
[-o offset] [-l
length] [-m minimum-free-extent]
[-v] mountpoint
add an example, a script, a trick and tips
examples
no example yet ...
... Feel free to add your own example above to help other Linux-lovers !
description
fstrim
is used on a mounted filesystem to discard (or
"trim") blocks which are not in use by the
filesystem. This is useful for solid-state drives (SSDs) and
thinly-provisioned storage.
By default,
fstrim will discard all unused blocks in the
filesystem. Options may be used to modify this behavior
based on range or size, as explained below.
The
mountpoint argument is the pathname of the directory
where the filesystem is mounted.
options
The
offset, length, and minimum-free-extent
arguments may be followed by binary (2^N) suffixes KiB, MiB,
GiB, TiB, PiB and EiB (the "iB" is optional, e.g.
"K" has the same meaning as "KiB") or
decimal (10^N) suffixes KB, MB, GB, PB and EB.
-h, --help
Print help and exit.
-o,
--offset offset
Byte offset in filesystem from
which to begin searching for free blocks to discard. Default
value is zero, starting at the beginning of the
filesystem.
-l,
--length length
Number of bytes after starting
point to search for free blocks to discard. If the specified
value extends past the end of the filesystem, fstrim
will stop at the filesystem size boundary. Default value
extends to the end of the filesystem.
-m,
--minimum minimum-free-extent
Minimum contiguous free range
to discard, in bytes. (This value is internally rounded up
to a multiple of the filesystem block size). Free ranges
smaller than this will be ignored. By increasing this value,
the fstrim operation will complete more quickly for
filesystems with badly fragmented freespace, although not
all blocks will be discarded. Default value is zero, discard
every free block.
-v,
--verbose
Verbose execution. When
specified fstrim will output the number of bytes
passed from the filesystem down the block stack to the
device for potential discard. This number is a maximum
discard amount from the storage device’s perspective,
because FITRIM ioctl called repeated will keep
sending the same sectors for discard repeatedly.
fstrim
will report the same potential discard bytes each time, but
only sectors which had been written to between the discards
would actually be discarded by the storage device. Further,
the kernel block layer reserves the right to adjust the
discard ranges to fit raid stripe geometry, non-trim capable
devices in a LVM setup, etc. These reductions would not be
reflected in fstrim_range.len (the --length
option).
availability
The fstrim command is part of the util-linux package and is
available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
see also
mount
author
Lukas Czerner
<lczerner[:at:]redhat[:dot:]com>
Karel Zak <kzak[:at:]redhat[:dot:]com>