Mon May 14 01:00:02 CST 2018
InnoDB Backup Utility v1.5.1-xtrabackup; Copyright 2003, 2009 Innobase Oy
and Percona LLC and/or its affiliates 2009-2013.  All Rights Reserved.
This software is published under
the GNU GENERAL PUBLIC LICENSE Version 2, June 1991.
180514 01:00:05  innobackupex: Connecting to MySQL server with DSN 'dbi:mysql:;mysql_read_default_file=/opt/mysql/my.cnf;mysql_read_default_group=xtrabackup;mysql_
socket=/opt/mysql/run/mysql.sock' (using password: NO).
180514 01:00:05  innobackupex: Connected to MySQL server
IMPORTANT: Please check that the backup run completes successfully.
           At the end of a successful backup run innobackupex
           prints "completed OK!".
innobackupex: Using mysql server version 5.6.21-70.0-log
innobackupex: Created backup directory /root
180514 01:00:05  innobackupex: Starting ibbackup with command: xtrabackup_56  --defaults-file="/opt/mysql/my.cnf"  --defaults-group="mysqld" --backup --suspend-at-
end --target-dir=/data/mysql/tmp --tmpdir=/data/mysql/tmp --throttle=10 --stream=tar
innobackupex: Waiting for ibbackup (pid=23547) to suspend
innobackupex: Suspend file '/data/mysql/tmp/xtrabackup_suspended_2'
xtrabackup_56 version 2.1.5 for Percona Server 5.1.70 unknown-linux-gnu (x86_64) (revision id: undefined)
xtrabackup: uses posix_fadvise().
xtrabackup: cd to /data/mysql/data
xtrabackup: using the following InnoDB configuration:
xtrabackup:   innodb_data_home_dir = ./
xtrabackup:   innodb_data_file_path = ibdata1:12M:autoextend
xtrabackup:   innodb_log_group_home_dir = ./
xtrabackup:   innodb_log_files_in_group = 2
xtrabackup:   innodb_log_file_size = 268435456
xtrabackup: using O_DIRECT
xtrabackup: error: log block numbers mismatch:
xtrabackup: error: expected log block no. 1013117100, but got no. 1014165668 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.
innobackupex: Error: The xtrabackup child process has died at /usr/bin/innobackupex line 2579.

1、redo log的文件大小（innodb_log_file_size*innodb_log_files_in_group）设置过小；
2、XtraBackup拷贝redo log的速度有些慢（可能受其他的系统任务的比较频繁的磁盘IO影响）；
3、如果备份文件是存储在远程文件系统上，则还有可能是受网络带宽较小或拥堵导致；

由于修改innodb_log_file_size的话需要重启mysqld服务，因此先调整定时备份任务的开始时间，错开IO高峰期。经测备份可以成功。
后面找停机窗口再调整redo参数。