这是因为当服务器或服务器框架交换出时，可以将一个单元旋转出生产而通过其他单元来处理负载，从而进行内存和CPU升级。

This is because a cell can be rotated out of production, with the other cells handling the load while servers or server frames are swapped out so that memory and CPU upgrades take place.

youdao

如果由于维护或者升级的原因需要移除一个单元，负载均衡器可以把流量直接发送到正在运行的那个单元。

If a cell needs to be removed for maintenance or an upgrade, the load balancer can be directed to send traffic to just the cell that is running.

youdao

用于批处理和“工作单元”请求的负载格式和语义。

Payload formats and semantics for batch and "unit of work" requests.

youdao