[GitHub/mt8127/android_kernel_alcatel_ttab.git] / Documentation / device-mapper / delay.txt

dm-delay
========

Device-Mapper's "delay" target delays reads and/or writes
and maps them to different devices.

Parameters:
    <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]

With separate write parameters, the first set is only used for reads.
Delays are specified in milliseconds.

Example scripts
===============
[[
#!/bin/sh
# Create device delaying rw operation for 500ms
echo "0 `blockdev --getsize $1` delay $1 0 500" | dmsetup create delayed
]]

[[
#!/bin/sh
# Create device delaying only write operation for 500ms and
# splitting reads and writes to different devices $1 $2
echo "0 `blockdev --getsize $1` delay $1 0 0 $2 0 500" | dmsetup create delayed
]]
Commit	Line	Data
26b9f228 HM	1	dm-delay
	2	========
	3
	4	Device-Mapper's "delay" target delays reads and/or writes
	5	and maps them to different devices.
	6
	7	Parameters:
	8	<device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
	9
	10	With separate write parameters, the first set is only used for reads.
	11	Delays are specified in milliseconds.
	12
	13	Example scripts
	14	===============
	15	[[
	16	#!/bin/sh
	17	# Create device delaying rw operation for 500ms
	18	echo "0 `blockdev --getsize $1` delay $1 0 500" \| dmsetup create delayed
	19	]]
	20
	21	[[
	22	#!/bin/sh
	23	# Create device delaying only write operation for 500ms and
	24	# splitting reads and writes to different devices $1 $2
	25	echo "0 `blockdev --getsize $1` delay $1 0 0 $2 0 500" \| dmsetup create delayed
	26	]]