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Documentation/device-mapper/dm-flakey.txt
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dm-flakey ========= |
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This target is the same as the linear target except that it exhibits unreliable behaviour periodically. It's been found useful in simulating failing devices for testing purposes. |
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Starting from the time the table is loaded, the device is available for |
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<up interval> seconds, then exhibits unreliable behaviour for <down interval> seconds, and then this cycle repeats. |
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Also, consider using this in combination with the dm-delay target too, which can delay reads and writes and/or send them to different underlying devices. Table parameters ---------------- <dev path> <offset> <up interval> <down interval> \ [<num_features> [<feature arguments>]] Mandatory parameters: |
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<dev path>: Full pathname to the underlying block-device, or a "major:minor" device-number. <offset>: Starting sector within the device. <up interval>: Number of seconds device is available. <down interval>: Number of seconds device returns errors. |
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Optional feature parameters: If no feature parameters are present, during the periods of unreliability, all I/O returns errors. drop_writes: All write I/O is silently ignored. Read I/O is handled correctly. |
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corrupt_bio_byte <Nth_byte> <direction> <value> <flags>: During <down interval>, replace <Nth_byte> of the data of each matching bio with <value>. <Nth_byte>: The offset of the byte to replace. Counting starts at 1, to replace the first byte. <direction>: Either 'r' to corrupt reads or 'w' to corrupt writes. 'w' is incompatible with drop_writes. <value>: The value (from 0-255) to write. <flags>: Perform the replacement only if bio->bi_rw has all the selected flags set. Examples: corrupt_bio_byte 32 r 1 0 - replaces the 32nd byte of READ bios with the value 1 corrupt_bio_byte 224 w 0 32 - replaces the 224th byte of REQ_META (=32) bios with the value 0 |