The goal of migrating is to upgrade your configuration to the new software version as smoothly as possibly.

这个句子是想表达 “尽可能顺利地升级” 这个意思。所以，as smoothly as possibly 是错误的，应改为：as smoothly as possible。这个语境决定了使用 as...as possible。

那么，有没有两个 as 之后都是形容词，或者两个 as 之后都是副词的情况呢？答案是肯定的。此用法表示同一个人或同一个事物，同时具备这两种品质。这时，as...as... 表示“既......又......”，等于both...and...的意思。

举例如下：

The girl is as shy as nervous. 这个女孩既害羞又紧张。

This method is as convenient as effcient. 这种方法既方便又有效。

He walks as fast as gracefully. 他走得又快又优雅。

She smiled as brightly as sincerely. 她笑得既灿烂又真诚。