summaryrefslogtreecommitdiff
path: root/Documentation/admin-guide/device-mapper/delay.rst
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/admin-guide/device-mapper/delay.rst')
-rw-r--r--Documentation/admin-guide/device-mapper/delay.rst31
1 files changed, 31 insertions, 0 deletions
diff --git a/Documentation/admin-guide/device-mapper/delay.rst b/Documentation/admin-guide/device-mapper/delay.rst
new file mode 100644
index 000000000000..917ba8c33359
--- /dev/null
+++ b/Documentation/admin-guide/device-mapper/delay.rst
@@ -0,0 +1,31 @@
+========
+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