1 ========= 2 dm-flakey 3 ========= 4 5 This target is the same as the linear target except that it exhibits 6 unreliable behaviour periodically. It's been found useful in simulating 7 failing devices for testing purposes. 8 9 Starting from the time the table is loaded, the device is available for 10 <up interval> seconds, then exhibits unreliable behaviour for <down 11 interval> seconds, and then this cycle repeats. 12 13 Also, consider using this in combination with the dm-delay target too, 14 which can delay reads and writes and/or send them to different 15 underlying devices. 16 17 Table parameters 18 ---------------- 19 20 :: 21 22 <dev path> <offset> <up interval> <down interval> \ 23 [<num_features> [<feature arguments>]] 24 25 Mandatory parameters: 26 27 <dev path>: 28 Full pathname to the underlying block-device, or a 29 "major:minor" device-number. 30 <offset>: 31 Starting sector within the device. 32 <up interval>: 33 Number of seconds device is available. 34 <down interval>: 35 Number of seconds device returns errors. 36 37 Optional feature parameters: 38 39 If no feature parameters are present, during the periods of 40 unreliability, all I/O returns errors. 41 42 error_reads: 43 All read I/O is failed with an error signalled. 44 Write I/O is handled correctly. 45 46 drop_writes: 47 All write I/O is silently ignored. 48 Read I/O is handled correctly. 49 50 error_writes: 51 All write I/O is failed with an error signalled. 52 Read I/O is handled correctly. 53 54 corrupt_bio_byte <Nth_byte> <direction> <value> <flags>: 55 During <down interval>, replace <Nth_byte> of the data of 56 each matching bio with <value>. 57 58 <Nth_byte>: 59 The offset of the byte to replace. 60 Counting starts at 1, to replace the first byte. 61 <direction>: 62 Either 'r' to corrupt reads or 'w' to corrupt writes. 63 'w' is incompatible with drop_writes. 64 <value>: 65 The value (from 0-255) to write. 66 <flags>: 67 Perform the replacement only if bio->bi_opf has all the 68 selected flags set. 69 70 random_read_corrupt <probability> 71 During <down interval>, replace random byte in a read bio 72 with a random value. probability is an integer between 73 0 and 1000000000 meaning 0% to 100% probability of corruption. 74 75 random_write_corrupt <probability> 76 During <down interval>, replace random byte in a write bio 77 with a random value. probability is an integer between 78 0 and 1000000000 meaning 0% to 100% probability of corruption. 79 80 Examples: 81 82 Replaces the 32nd byte of READ bios with the value 1:: 83 84 corrupt_bio_byte 32 r 1 0 85 86 Replaces the 224th byte of REQ_META (=32) bios with the value 0:: 87 88 corrupt_bio_byte 224 w 0 32
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.