They played alongside Muddy Waters for 10 years, before launching The Legendary Blues Band with three other members of Muddy's backup group.

VOA: standard.2010.07.20

SRC back One is called SRC for Source and one is called SRC.back which was my backup of today's source code in case I screw up.

其中一个叫SRC，用来装源代码，另一个叫,用来备份源代码，以防我搞砸了。

哈佛公开课 - 计算机科学课程节选

You really need that because if you have only one copy of something, you don't have a backup; so, you can store the one copy separately.

你真的很需要这项发明,因为要是你只有一份的话，你就没有备份;,这样的话，你就可以将副本单独留存。

耶鲁公开课 - 金融市场课程节选