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authorMauro Carvalho Chehab <mchehab+samsung@kernel.org>2019-06-18 18:40:23 +0300
committerMauro Carvalho Chehab <mchehab+samsung@kernel.org>2019-07-15 17:03:01 +0300
commit6cf2a73cb2bc422a03984b285a63632c27f8c4e4 (patch)
treecb508e0a180ce350a86842353c5cb417e560835b /Documentation/admin-guide/device-mapper/delay.rst
parent159a5e78bdcabb1f87ee5536182a99a307ae0bac (diff)
downloadlinux-6cf2a73cb2bc422a03984b285a63632c27f8c4e4.tar.xz
docs: device-mapper: move it to the admin-guide
The DM support describes lots of aspects related to mapped disk partitions from the userspace PoV. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
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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>
+ [<flush_device> <flush_offset> <flush_delay>]]
+
+With separate write parameters, the first set is only used for reads.
+Offsets are specified in sectors.
+Delays are specified in milliseconds.
+
+Example scripts
+===============
+
+::
+
+ #!/bin/sh
+ # Create device delaying rw operation for 500ms
+ echo "0 `blockdev --getsz $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 --getsz $1` delay $1 0 0 $2 0 500" | dmsetup create delayed