When portage tries to get a file from a server that is down, it tries however many times then moves on to a different server. If you do another emerge right after that, it will still try the inaccessable server. This slows down the emerge, and clutters the console. Reproducible: Always Steps to Reproduce: 1. Emerge a package so that portage tried to get the files from a server that is down 2. Emerge another package right after that. Actual Results: Portage still tries to get files from the server that is down. Expected Results: Portage should put the server on a sort of "blacklist" of inaccessable servers that will not be used. Those servers should remain on the list for a certain period of time (say one hour) before they are removed.
Cahnge your GENTOO_MIRRORS setting if you encounter a mirror that is down. There is no way for portage to say WHY a file couldn't be downloaded (as that's done by an external program specified in FECTHCOMMAND), so we can't differ if the file is not on a mirror, the given mirror is down or you have a local network problem. (and checking the exit code doesn't work as different commands have different exitcodes).
If the file can't be downloaded and it is not caused by a local network problem, then it is not very useful to try to get files from that server.
as I said, we can't check why it failed. Also if a mirror fails for one file that doesn't mean that it would fail for a different one.