Documentation/device-mapper/delay.txt

   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                                [<flush_device> <flush_offset> <flush_delay>]]
  10
  11 With separate write parameters, the first set is only used for reads.
  12 Offsets are specified in sectors.
  13 Delays are specified in milliseconds.
  14
  15 Example scripts
  16 ===============
  17 [[
  18 #!/bin/sh
  19 # Create device delaying rw operation for 500ms
  20 echo "0 `blockdev --getsz $1` delay $1 0 500" | dmsetup create delayed
  21 ]]
  22
  23 [[
  24 #!/bin/sh
  25 # Create device delaying only write operation for 500ms and
  26 # splitting reads and writes to different devices $1 $2
  27 echo "0 `blockdev --getsz $1` delay $1 0 0 $2 0 500" | dmsetup create delayed
  28 ]]