We are still using the "semi"-online backup solution which requires a
downtime for about 20 to 30 minutes.

Reason: we were told that there may be some problems in getting a REAL
consistent backup using true-online. To minimize the risk, we kept the
"old" solution (also having mirrored disk in place. But a backup here also
requires a down-time to split the volume, and requires some time afterwards
to synchronize the mirror).

Best regards, Andreas Schmidt, CSC, Germany