also: ミラーサーバ
noun
mirror server
A server that holds a copy of data from another server, used to reduce load or provide redundancy.
このファイルはミラーサーバーからダウンロードできます。
You can download this file from the mirror server.
ミラーリング refers to the act or process of mirroring data, while ミラーサーバー is the server that performs or hosts the mirrored copy.
Borrowed from English 'mirror server'.