Documentation/admin-guide/device-mapper/delay.rst

   1 ========
   2 dm-delay
   3 ========
   4
   5 Device-Mapper's "delay" target delays reads and/or writes
   6 and maps them to different devices.
   7
   8 Parameters::
   9
  10     <device> <offset> <delay> [<write_device> <write_offset> <write_delay>
  11                                [<flush_device> <flush_offset> <flush_delay>]]
  12
  13 With separate write parameters, the first set is only used for reads.
  14 Offsets are specified in sectors.
  15 Delays are specified in milliseconds.
  16
  17 Example scripts
  18 ===============
  19
  20 ::
  21
  22         #!/bin/sh
  23         # Create device delaying rw operation for 500ms
  24         echo "0 `blockdev --getsz $1` delay $1 0 500" | dmsetup create delayed
  25
  26 ::
  27
  28         #!/bin/sh
  29         # Create device delaying only write operation for 500ms and
  30         # splitting reads and writes to different devices $1 $2
  31         echo "0 `blockdev --getsz $1` delay $1 0 0 $2 0 500" | dmsetup create delayed