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fstrim(8) [centos man page]

FSTRIM(8)						       System Administration							 FSTRIM(8)

NAME
fstrim - discard unused blocks on a mounted filesystem SYNOPSIS
fstrim [-o offset] [-l length] [-m minimum-free-extent] [-v] mountpoint 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 the multiplicative suffixes KiB=1024, MiB=1024*1024, and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional, e.g. "K" has the same meaning as "KiB") or the suffixes KB=1000, MB=1000*1000, and so on for GB, TB, PB, EB, ZB and YB. -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 begin- ning 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). AUTHOR
Lukas Czerner <lczerner@redhat.com> Karel Zak <kzak@redhat.com> SEE ALSO
mount(8) AVAILABILITY
The fstrim command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/. util-linux November 2010 FSTRIM(8)

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BLKDISCARD(8)						       System Administration						     BLKDISCARD(8)

NAME
blkdiscard - discard sectors on a device SYNOPSIS
blkdiscard [-o offset] [-l length] [-s] [-v] device DESCRIPTION
blkdiscard is used to discard device sectors. This is useful for solid-state drivers (SSDs) and thinly-provisioned storage. Unlike fstrim(8) this command is used directly on the block device. By default, blkdiscard will discard all blocks on the device. Options may be used to modify this behavior based on range or size, as explained below. The device argument is the pathname of the block device. WARNING: All data in the discarded region on the device will be lost! OPTIONS
The offset and length arguments may be followed by the multiplicative suffixes KiB=1024, MiB=1024*1024, and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional, e.g., "K" has the same meaning as "KiB") or the suffixes KB=1000, MB=1000*1000, and so on for GB, TB, PB, EB, ZB and YB. -h, --help Print help and exit. -o, --offset offset Byte offset in the device from which to discard. Provided value will be aligned to the device sector size. Default value is zero. -l, --length length Number of bytes after starting point to discard. Provided value will be aligned to the device sector size. If the specified value extends past the end of the device, blkdiscard will stop at the device size boundary. Default value extends to the end of the device. -s, --secure Perform secure discard. Secure discard is the same as regular discard except all copies of the discarded blocks possibly created by garbage collection must also be erased. It has to be supported by the device. -v, --verbose Print aligned offset and length arguments. AUTHOR
Lukas Czerner <lczerner@redhat.com> SEE ALSO
fstrim(8) AVAILABILITY
The blkdiscard command is part of the util-linux package and is available Linux Kernel Archive <ftp://ftp.kernel.org/pub/linux/utils/util- linux/>. util-linux October 2012 BLKDISCARD(8)
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