1、DDL操作与Xtrabackup备份冲突
当MySQL使用xrabckup进行备份时，如果执行DDL进行表修改，会导致xrabckup备份失败。
错误类似于：
InnoDB: Last flushed lsn: 3375345258517 load_index lsn 3379255303757
InnoDB: An optimized (without redo logging) DDLoperation has been performed. All modified pages may not have been flushed to the disk yet.
PXB will not be able take a consistent backup. Retry the backup operation
2、磁盘性能太差导致xtrabckup备份失败
Innodb产生日志的速度远超于Xtrabackup复制的速度，部分Innodb日志被截断，导致备份失败。
错误类似于：
xtrabackup: error: log block numbers mismatch:
xtrabackup: error: expected log block no. 201901064, but got no. 208192508 from the log file.
xtrabackup: error: it looks like InnoDB log has wrapped around before xtrabackup could process all records due to either log copying being too slow, or log files being too small.
xtrabackup: Error: xtrabackup_copy_logfile() failed.
