This bug will never be completely fixed WRT the 'mirror' segment type and snapshots. However, 'raid1' can be used in place of 'mirror' and does not suffer from this issue.
Thus, this becomes a documentation and awareness issue. I am marking this bug as MODIFIED, although that is not technically correct. I don't want to CLOSE the bug without the release note stating that users should use the alternative.
It could be argued that LVM should warn users if snapshots are attempted on 'mirror's and suggest 'raid1' instead...
Doc only bug, this should appear as a "Known Issue" item in the 6.4 documentation.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.