The failure rate of cisco router is extremely small, if you want to keep a secondary CME that's ok, but the easier way is that in case of failure you move circuits from one box to another. Having the PRI connected to two different boxes involves more configuration. However it can be done a pots and voip DP. If you do not have experience in configuring voip I recommend you hire a professional to save you time and frustration.
These are the paths to get to each CCX logs through CLI. They may be helpful if you are having issues accessing RTMT or downloading logs through it.
If you want to download them you have to prefix "file get " and you can add one of the options (re...