FAQ :

What does MIRROR1 and MIRROR2 mean?

Answer :

OPS Systems gives you an option to choose which server to download your packages from.
Our web servers (called MIRROR1 & MIRROR2) are located in different geographical areas which means you may get different download speeds depending on where you are located.
You can pick either MIRROR1 or MIRROR2. If the speed of download is slow, cancel the download and pick the other MIRROR server.

Sometimes, one of the servers may be off-line and the download link will be temporarily broken. If that is the case, pick the other MIRROR server.