备份可以通过两种不同的方法启动。There are two different methods by which the backup may be started.

将集群备份文件复制到正在上线的副本。每个运行源集群的 ndbd 进程的系统上都有集群备份文件，所有这些文件必须复制到副本上以确保恢复成功。备份文件可以复制到副本管理主机所在计算机的任何目录，只要 MySQL 和 NDB 二进制文件在该目录有读取权限。在本例中，我们假设这些文件已被复制到目录 /var/BACKUPS/BACKUP-1。Copy the cluster backup files to the replica that is being brought on line. Each system running an ndbd process for the source cluster has cluster backup files located on it, and all of these files must be copied to the replica to ensure a successful restore. The backup files can be copied into any directory on the computer where the replica's management host resides, as long as the MySQL and NDB binaries have read permissions in that directory. In this case, we assume that these files have been copied into the directory /var/BACKUPS/BACKUP-1.

While it is not necessary that the replica cluster have the same number of data nodes as the source, it is highly recommended this number be the same. It is necessary that the replication process is prevented from starting when the replica server starts. You can do this by starting the replica with --skip-replica-start.

在复制集群上创建源集群中存在且需要复制的任何数据库。Create any databases on the replica cluster that are present on the source cluster and that are to be replicated.

使用 mysql 客户端中的此语句重置副本集群：Reset the replica cluster using this statement in the mysql client:

mysqlR> RESET REPLICA;

现在，您可以在副本上使用 ndb_restore 命令依次对每个备份文件启动集群恢复过程。对于第一个备份文件，需要包括 -m 选项以恢复集群元数据，如下所示：You can now start the cluster restoration process on the replica using the ndb_restore command for each backup file in turn. For the first of these, it is necessary to include the -m option to restore the cluster metadata, as shown here:

shellR> ndb_restore -c replica_host:port -n node-id \
        -b backup-id -m -r dir

dir is the path to the directory where the backup files have been placed on the replica. For the ndb_restore commands corresponding to the remaining backup files, the -m option should 在多线程系统中 be used.dir is the path to the directory where the backup files have been placed on the replica. For the ndb_restore commands corresponding to the remaining backup files, the -m option should not be used.

要从一个具有四个数据节点的源集群（如图所示，见第 25.7 节，“NDB 集群复制”）进行恢复，并且备份文件已复制到目录/var/BACKUPS/BACKUP-1，在副本上执行的正确命令顺序可能如下所示：For restoring from a source cluster with four data nodes (as shown in the figure in Section 25.7, “NDB Cluster Replication”) where the backup files have been copied to the directory /var/BACKUPS/BACKUP-1, the proper sequence of commands to be executed on the replica might look like this:

shellR> ndb_restore -c replica-host:1186 -n 2 -b 1 -m \
        -r ./var/BACKUPS/BACKUP-1
shellR> ndb_restore -c replica-host:1186 -n 3 -b 1 \
        -r ./var/BACKUPS/BACKUP-1
shellR> ndb_restore -c replica-host:1186 -n 4 -b 1 \
        -r ./var/BACKUPS/BACKUP-1
shellR> ndb_restore -c replica-host:1186 -n 5 -b 1 -e \
        -r ./var/BACKUPS/BACKUP-1

现在你需要从副本的 ndb_apply_status 表中获取最新的周期（如 第 25.7.8 节，“使用 NDB 集群复制实现故障切换” 中所讨论）：Now you need to obtain the most recent epoch from the ndb_apply_status table on the replica (as discussed in Section 25.7.8, “Implementing Failover with NDB Cluster Replication”):

mysqlR> SELECT @latest:=MAX(epoch)
        FROM mysql.ndb_apply_status;

使用在上一步中获取的 @latest 作为周期值，你可以从源端的 mysql.ndb_binlog_index 表中获取正确二进制日志文件 @file 中的正确起始位置 @pos。这里显示的查询从逻辑恢复位置之前应用的最后一个周期的 Position 和 File 列中获取这些信息：Using @latest as the epoch value obtained in the previous step, you can obtain the correct starting position @pos in the correct binary log file @file from the mysql.ndb_binlog_index table on the source. The query shown here gets these from the Position and File columns from the last epoch applied before the logical restore position:

mysqlS> SELECT
     ->     @file:=SUBSTRING_INDEX(File, '/', -1),
     ->     @pos:=Position
     -> FROM mysql.ndb_binlog_index
     -> WHERE epoch > @latest
     -> ORDER BY epoch ASC LIMIT 1;

如果当前没有复制流量，您可以通过在源端运行 SHOW BINARY LOG STATUS 来获取类似信息，并使用输出中 Position 列显示的值，对于在 File 列中所有文件显示的具有最大后缀值的文件名。在这种情况下，您必须确定这是哪个文件，并在下一步手动提供名称或通过脚本解析输出。In the event that there is currently no replication traffic, you can get similar information by running SHOW BINARY LOG STATUS on the source and using the value shown in the Position column of the output for the file whose name has the suffix with the greatest value for all files shown in the File column. In this case, you must determine which file this is and supply the name in the next step manually or by parsing the output with a script.

使用上一步中获得的值，您现在可以在副本的mysql客户端中发出相应的命令。使用以下CHANGE REPLICATION SOURCE TO语句：Using the values obtained in the previous step, you can now issue the appropriate in the replica's mysql client. Use the following CHANGE REPLICATION SOURCE TO statement:

mysqlR> CHANGE REPLICATION SOURCE TO
     ->     SOURCE_LOG_FILE='@file',
     ->     SOURCE_LOG_POS=@pos;

现在副本知道从哪个二进制日志文件的哪个位置开始读取源数据，您可以使用此语句使副本开始复制：Now that the replica knows from what point in which binary log file to start reading data from the source, you can cause the replica to begin replicating with this statement:

mysqlR> START REPLICA;