Use a mirrored mirror log

By default, LVM will sync the two mirrors of a logical volume on
creation. This is I/O intensive and it takes a long time though, so we
tell it not to with --nosync. The next default behavior is to create a
mirror log which says what portions of the mirrors are in sync. But
then if a disk backing a mirror log fails, we have to deal with
resyncing the mirrors at each reboot.

This commit tells LVM to use a mirrored mirror log, which will use
approximately 4MB of extra space, but means we'll never have to
sync mirrors, ever.

Change-Id: I6586ced4e7e66ae79ae134406a4c633f8fbc8602

diff --git a/cinder/brick/local_dev/lvm.py b/cinder/brick/local_dev/lvm.py
index 0037632b2383b7d3d98d2ff00dfd5252a95c9c09..17602e99852de837f3071a6a8554a818391a37f5 100644 (file)
--- a/cinder/brick/local_dev/lvm.py
+++ b/cinder/brick/local_dev/lvm.py
@@ -472,7 +472,8 @@ class LVM(executor.Executor):
             cmd = ['lvcreate', '-n', name, self.vg_name, '-L', size_str]
 
         if mirror_count > 0:
-            cmd.extend(['-m', mirror_count, '--nosync'])
+            cmd.extend(['-m', mirror_count, '--nosync',
+                        '--mirrorlog mirrored'])
             terras = int(size_str[:-1]) / 1024.0
             if terras >= 1.5:
                 rsize = int(2 ** math.ceil(math.log(terras) / math.log(2)))