There's the main cooling system, a backup to it, a backup to the backup, a backup to the backup to the backup, and so on.

首先有一个主冷却系统，然后有一个备用系统，备用系统还有一个备用系统，再有一个备用系统的备用系统，如此下去。

youdao

For offline backup, the exclusive use is required to do a backup whereas online backup allow users to connect while backup is in progress.

对于脱机备份，需要排它地进行备份，联机备份则允许用户在备份过程中连接数据库。

youdao

The backup process is not a file system backup; it is a logical backup.

这种备份不是文件系统的备份，而是逻辑上的备份。

youdao

They were recorded with excellent backup singers and musicians.

VOA: special.2009.05.11

But it's more limited in its feature set but again will build backup to those features.

由于其自身的特点而很受限制,但是可以对这些特征进行备份。

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So it's like a backup.

所以，这就像是备用。

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