1 ======== 1 ========
2 dm-delay 2 dm-delay
3 ======== 3 ========
4 4
5 Device-Mapper's "delay" target delays reads an 5 Device-Mapper's "delay" target delays reads and/or writes
6 and/or flushs and optionally maps them to diff !! 6 and maps them to different devices.
7 7
8 Arguments:: !! 8 Parameters::
9 9
10 <device> <offset> <delay> [<write_device> 10 <device> <offset> <delay> [<write_device> <write_offset> <write_delay>
11 [<flush_device> 11 [<flush_device> <flush_offset> <flush_delay>]]
12 12
13 Table line has to either have 3, 6 or 9 argume !! 13 With separate write parameters, the first set is only used for reads.
14 <<
15 3: apply offset and delay to read, write and f <<
16 <<
17 6: apply offset and delay to device, also appl <<
18 to write and flush operations on optionally <<
19 optionally different sector offset <<
20 <<
21 9: same as 6 arguments plus define flush_offse <<
22 on/with optionally different flush_device/f <<
23 <<
24 Offsets are specified in sectors. 14 Offsets are specified in sectors.
25 <<
26 Delays are specified in milliseconds. 15 Delays are specified in milliseconds.
27 16
28 <<
29 Example scripts 17 Example scripts
30 =============== 18 ===============
31 19
32 :: 20 ::
33 #!/bin/sh <<
34 # <<
35 # Create mapped device named "delayed" <<
36 # <<
37 dmsetup create delayed --table "0 `bl <<
38 21
39 :: <<
40 #!/bin/sh 22 #!/bin/sh
41 # !! 23 # Create device delaying rw operation for 500ms
42 # Create mapped device delaying write !! 24 echo "0 `blockdev --getsz $1` delay $1 0 500" | dmsetup create delayed
43 # splitting reads to device $1 but wri <<
44 # to different offsets of 2048 and 409 <<
45 # <<
46 dmsetup create delayed --table "0 `blo <<
47 25
48 :: 26 ::
>> 27
49 #!/bin/sh 28 #!/bin/sh
50 # !! 29 # Create device delaying only write operation for 500ms and
51 # Create mapped device delaying reads !! 30 # splitting reads and writes to different devices $1 $2
52 # onto the same backing device at offs !! 31 echo "0 `blockdev --getsz $1` delay $1 0 0 $2 0 500" | dmsetup create delayed
53 # <<
54 dmsetup create delayed --table "0 `blo <<
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