原理
percona xtrabackup备份过程主要分为以下几点：
1、xtrabackup在启动时会记住LSN(log sequence number)，然后复制所有的数据文件
2、xtrabackup会运行一个后台进程，用于监控事务日志(redo.log)，并从事务日志中复制最新的修改
3、准备过程(prepare)，xtrabackup使用之前复制的事务日志，对各个数据文件执行灾难恢复
4、执行flush tables with read lock来阻止新的写入进来，并把MyISAM表数据刷写到硬盘上，之后复制MyISAM数据文件，最后释放锁。
其中1-3步骤是xtrabackup来实现，第4步由innobackupex来实现。
备份MyISAM和Innodb表最终会处于一致，在prepare过程结束后，Innodb表数据已经前滚到整个备份数据结束的点，而不是回滚到xtrabackuo刚开始的点。
通过复制数据文件、日志文件和提交日志到数据文件（前滚）实现各种复合备份方式。
innobackupex备份对MyISAM表之前要对全库进行加READ LOCK，阻塞写操作，对Innodb表备份不会阻塞读写。
备份演练
、创建备份目录
mkdir -p /data1/backup 、拷贝全量数据
innobackupex --defaults-file=/data1/mysql6011/my6011.cnf --user=root --password='xxx' --tmpdir=/data1/tmp/ --socket=/tmp/mysql6011.sock --no-timestamp --slave-info /data1/backup/mysql6011 > innobackupex.log >& 注意点：
a、设置tmp为目录较大的位置
b、设置no-timestamp，否则以时间作为前缀
c、设置备份的目录,/data1/backup先提前创建好，然后再以mysql6011作为备份的目录名称
d、配置文件中character_set_client=utf8,导致错误 、拷贝配置文件到另一台机器上 4、回放redolog(apply-log)
如果给主库搭建从库：
http://www.percona.com/doc/percona-xtrabackup/2.1/howtos/setting_up_replication.html
binlog点的位置为xtrabackup_binlog_info文件中
apply-lo*生的日志：
[root@eos177 data1]# innobackupex -defaults-file=/data1/mysql6011/my6011.cnf --apply-log /data1/mysql6011/ InnoDB Backup Utility v1.5.1-xtrabackup; Copyright , Innobase Oy
and Percona Inc -. All Rights Reserved. This software is published under
the GNU GENERAL PUBLIC LICENSE Version , June . IMPORTANT: Please check that the apply-log run completes successfully.
At the end of a successful apply-log run innobackupex
prints "completed OK!". :: innobackupex: Starting ibbackup with command: xtrabackup_55 --defaults-file="/data1/mysql6011/my6011.cnf" --prepare --target-dir=/data1/mysql6011 xtrabackup_55 version 1.6. for Percona Server 5.5. Linux (x86_64) (revision id: )
xtrabackup: cd to /data1/mysql6011
xtrabackup: This target seems to be not prepared yet.
xtrabackup: xtrabackup_logfile detected: size=, start_lsn=()
xtrabackup: Temporary instance for recovery is set as followings.
xtrabackup: innodb_data_home_dir = ./
xtrabackup: innodb_data_file_path = ibdata1:100M:autoextend
xtrabackup: innodb_log_group_home_dir = ./
xtrabackup: innodb_log_files_in_group =
xtrabackup: innodb_log_file_size =
:: InnoDB: Using Linux native AIO
xtrabackup: Starting InnoDB instance for recovery.
xtrabackup: Using bytes for buffer pool (set by --use-memory parameter)
:: InnoDB: The InnoDB memory heap is disabled
:: InnoDB: Mutexes and rw_locks use GCC atomic builtins
:: InnoDB: Compressed tables use zlib 1.2.
:: InnoDB: Using Linux native AIO
:: InnoDB: Warning: innodb_file_io_threads is deprecated. Please use innodb_read_io_threads and innodb_write_io_threads instead
:: InnoDB: Initializing buffer pool, size = 100.0M
:: InnoDB: Completed initialization of buffer pool
:: InnoDB: highest supported file format is Barracuda.
InnoDB: Log scan progressed past the checkpoint lsn
:: InnoDB: Database was not shut down normally!
InnoDB: Starting crash recovery.
InnoDB: Reading tablespace information from the .ibd files...
InnoDB: Doing recovery: scanned up to log sequence number ( %)
:: InnoDB: Starting an apply batch of log records to the database...
InnoDB: Progress in percents:
InnoDB: Apply batch completed
InnoDB: Last MySQL binlog file position , file name ./mysql-bin.
:: InnoDB: Waiting for the background threads to start
:: Percona XtraDB (http://www.percona.com) 1.1.5-20.0 started; log sequence number 37043837591 [notice (again)]
If you use binary log and don't use any hack of group commit,
the binary log position seems to be:
InnoDB: Last MySQL binlog file position , file name ./mysql-bin. xtrabackup: starting shutdown with innodb_fast_shutdown =
:: InnoDB: Starting shutdown...
:: InnoDB: Shutdown completed; log sequence number :: innobackupex: Restarting xtrabackup with command: xtrabackup_55 --defaults-file="/data1/mysql6011/my6011.cnf" --prepare --target-dir=/data1/mysql6011
for creating ib_logfile* xtrabackup_55 version 1.6. for Percona Server 5.5. Linux (x86_64) (revision id: )
xtrabackup: cd to /data1/mysql6011
xtrabackup: This target seems to be already prepared.
xtrabackup: notice: xtrabackup_logfile was already used to '--prepare'.
xtrabackup: Temporary instance for recovery is set as followings.
xtrabackup: innodb_data_home_dir = ./
xtrabackup: innodb_data_file_path = ibdata1:100M:autoextend
xtrabackup: innodb_log_group_home_dir = ./
xtrabackup: innodb_log_files_in_group =
xtrabackup: innodb_log_file_size =
:: InnoDB: Using Linux native AIO
xtrabackup: Starting InnoDB instance for recovery.
xtrabackup: Using bytes for buffer pool (set by --use-memory parameter)
:: InnoDB: The InnoDB memory heap is disabled
:: InnoDB: Mutexes and rw_locks use GCC atomic builtins
:: InnoDB: Compressed tables use zlib 1.2.
:: InnoDB: Using Linux native AIO
:: InnoDB: Warning: innodb_file_io_threads is deprecated. Please use innodb_read_io_threads and innodb_write_io_threads instead
:: InnoDB: Initializing buffer pool, size = 100.0M
:: InnoDB: Completed initialization of buffer pool
:: InnoDB: Log file ./ib_logfile0 did not exist: new to be created
InnoDB: Setting log file ./ib_logfile0 size to MB
InnoDB: Database physically writes the file full: wait...
InnoDB: Progress in MB:
:: InnoDB: Log file ./ib_logfile1 did not exist: new to be created
InnoDB: Setting log file ./ib_logfile1 size to MB
InnoDB: Database physically writes the file full: wait...
InnoDB: Progress in MB:
:: InnoDB: Log file ./ib_logfile2 did not exist: new to be created
InnoDB: Setting log file ./ib_logfile2 size to MB
InnoDB: Database physically writes the file full: wait...
InnoDB: Progress in MB:
:: InnoDB: highest supported file format is Barracuda.
InnoDB: The log sequence number in ibdata files does not match
InnoDB: the log sequence number in the ib_logfiles!
:: InnoDB: Database was not shut down normally!
InnoDB: Starting crash recovery.
InnoDB: Reading tablespace information from the .ibd files...
InnoDB: Last MySQL binlog file position , file name ./mysql-bin.
:: InnoDB: Waiting for the background threads to start
:: Percona XtraDB (http://www.percona.com) 1.1.5-20.0 started; log sequence number 37043847180 [notice (again)]
If you use binary log and don't use any hack of group commit,
the binary log position seems to be:
InnoDB: Last MySQL binlog file position , file name ./mysql-bin. xtrabackup: starting shutdown with innodb_fast_shutdown =
:: InnoDB: Starting shutdown...
:: InnoDB: Shutdown completed; log sequence number
:: innobackupex: completed OK!
copy-back
innobackupex: Error: Original data directory '/data1/mysql6011' does not exist! at /etc/dbCluster/innobackupex line .
[root@eos177 data1]# innobackupex -defaults-file=/data1/backup/mysql6011/my6011.cnf /data1/backup/mysql6011 --copy-back InnoDB Backup Utility v1.5.1-xtrabackup; Copyright , Innobase Oy
and Percona Inc -. All Rights Reserved. This software is published under
the GNU GENERAL PUBLIC LICENSE Version , June . IMPORTANT: Please check that the copy-back run completes successfully.
At the end of a successful copy-back run innobackupex
prints "completed OK!". innobackupex: Starting to copy MyISAM tables, indexes,
innobackupex: .MRG, .TRG, .TRN, .ARM, .ARZ, .CSM, .CSV, .opt, and .frm files
innobackupex: in '/data1/backup/mysql6011'
innobackupex: back to original data directory '/data1/mysql6011'
innobackupex: Copying directory '/data1/backup/mysql6011/performance_schema'
innobackupex: Copying file '/data1/backup/mysql6011/xtrabackup_checkpoints'
innobackupex: Copying file '/data1/backup/mysql6011/xtrabackup_slave_info'
innobackupex: Copying directory '/data1/backup/mysql6011/mysql'
innobackupex: Copying file '/data1/backup/mysql6011/xtrabackup_binary'
innobackupex: Copying file '/data1/backup/mysql6011/xtrabackup_binlog_info'
innobackupex: Copying directory '/data1/backup/mysql6011/zjmdmm'
innobackupex: Copying file '/data1/backup/mysql6011/my6011.cnf'
innobackupex: Copying directory '/data1/backup/mysql6011/elink'
innobackupex: Copying file '/data1/backup/mysql6011/xtrabackup_binlog_pos_innodb'
innobackupex: Copying directory '/data1/backup/mysql6011/test' innobackupex: Starting to copy InnoDB tables and indexes
innobackupex: in '/data1/backup/mysql6011'
innobackupex: back to original InnoDB data directory '/data1/mysql6011'
innobackupex: Copying file '/data1/backup/mysql6011/ibdata1' innobackupex: Starting to copy InnoDB log files
innobackupex: in '/data1/backup/mysql6011'
innobackupex: back to original InnoDB log directory '/data1/mysql6011'
innobackupex: Copying file '/data1/backup/mysql6011/ib_logfile0'
innobackupex: Copying file '/data1/backup/mysql6011/ib_logfile2'
innobackupex: Copying file '/data1/backup/mysql6011/ib_logfile1'
innobackupex: Finished copying back files. :: innobackupex: completed OK!