From b26f5e3d7127487e934758c1fbe05d683b082cb0 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Tue, 2 Aug 2011 12:32:05 +0100 Subject: dm flakey: add drop_writes Add 'drop_writes' option to drop writes silently while the device is 'down'. Reads are not touched. Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon --- Documentation/device-mapper/dm-flakey.txt | 29 +++++++++++++++++++++++------ 1 file changed, 23 insertions(+), 6 deletions(-) (limited to 'Documentation') diff --git a/Documentation/device-mapper/dm-flakey.txt b/Documentation/device-mapper/dm-flakey.txt index c8efdfd19a65..1b66c868ee7e 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 - seconds, then returns errors for seconds, -and then this cycle repeats. + seconds, then exhibits unreliable behaviour for seconds, and then this cycle repeats. -Parameters: +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 +---------------- + \ + [ []] + +Mandatory parameters: : Full pathname to the underlying block-device, or a "major:minor" device-number. : Starting sector within the device. : Number of seconds device is available. : 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. -- cgit v1.2.3