Tài liệu High Availability MySQL Cookbook phần 4

By default, an online backup of a MySQL Cluster takes a consistent backup across all nodes
at the end of the process. This means that if you had two different clusters and ran an online
backup at the same time, the backup would not take place at exactly the same time. The
difference between the two backups would be a function of the backup duration, which
depends on various factors such as the performance of the node and the amount of data to
backup. This also means that if you required a backup of a cluster at an exact time, you can
only guess how long a backup will take and try to configure a backup at the right time.