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authorJosef Bacik2011-03-24 13:54:24 +0000
committerAlasdair G Kergon2011-03-24 13:54:24 +0000
commit3407ef5262b55ca5d7139d2b555ef792fe531eec (patch)
treefb5e083851c636e515095bb3eb90325f4b175129 /Documentation/device-mapper
parent024d37e95ec4a7ccc256973ab2feab01f4fbdd2d (diff)
dm: add flakey target
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. I needed a dm target to do some failure testing on btrfs's raid code, and Mike pointed me at this. Signed-off-by: Josef Bacik <josef@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
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diff --git a/Documentation/device-mapper/dm-flakey.txt b/Documentation/device-mapper/dm-flakey.txt
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+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.
+
+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.
+
+Parameters: <dev path> <offset> <up interval> <down interval>
+ <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.