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authorHeinz Mauelshagen <mauelshagen@redhat.com>2007-05-09 02:33:06 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-09 12:30:47 -0700
commit26b9f228703f0518a90e7513d6fe7b6abeed5138 (patch)
tree3437e92667c338ea46ad47b064ce4908d7d75fe2 /Documentation
parent0ba699347e96b5468b42b3decf1f381abbf99652 (diff)
downloadlinux-26b9f228703f0518a90e7513d6fe7b6abeed5138.tar.gz
dm: delay target
New device-mapper target that can delay I/O (for testing). Reads can be separated from writes, redirected to different underlying devices and delayed by differing amounts of time. Signed-off-by: Heinz Mauelshagen <mauelshagen@redhat.com> Signed-off-by: Milan Broz <mbroz@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/device-mapper/delay.txt26
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diff --git a/Documentation/device-mapper/delay.txt b/Documentation/device-mapper/delay.txt
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+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
+]]