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Diffstat (limited to 'Documentation/device-mapper/dm-flakey.txt')
| -rw-r--r-- | Documentation/device-mapper/dm-flakey.txt | 29 |
1 files changed, 23 insertions, 6 deletions
diff --git a/Documentation/device-mapper/dm-flakey.txt b/Documentation/device-mapper/dm-flakey.txt index c8efdfd19a6..1b66c868ee7 100644 --- a/Documentation/device-mapper/dm-flakey.txt +++ b/Documentation/device-mapper/dm-flakey.txt @@ -1,17 +1,34 @@ dm-flakey ========= -This target is the same as the linear target except that it returns I/O -errors periodically. It's been found useful in simulating failing -devices for testing purposes. +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. Starting from the time the table is loaded, the device is available for -<up interval> seconds, then returns errors for <down interval> seconds, -and then this cycle repeats. +<up interval> seconds, then exhibits unreliable behaviour for <down +interval> seconds, and then this cycle repeats. -Parameters: <dev path> <offset> <up interval> <down interval> +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: <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. + +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. |