domain controller FAILOVER -- Windows Server 2012 R2 ?

My two 50-user locations are connected via
 20MB fiber and each has ONE domain controller.

 I setup so if an ON-SITE domain controller
 is down it uses the REMOTE domain controller,
 but that does not work if the INTERNET
 between these two locations is down.

 I assume I could setup
    ** two domain controllers at location #1 and
    ** two domain controllers at location #2 ?

 If not, what do you recommend as a DC backup ?
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Lee W, MVPTechnology and Business Process AdvisorCommented:
Yes, you COULD do that.  But what are the odds you're going to have a DC down AND your internet down?  My DCs... and those at my clients are running 99.9% of the time.  The internet is probably 99.8% of the time.

For 50 user locations I MIGHT do two DCs at each (definitely one).  it really depends on how reliable the internet is and how reliable the servers are (they REALLY should be reliable or you're buying the wrong servers).

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Neil RussellTechnical Development LeadCommented:
As Lee stated, its all down to probability and risk.  IF your internet is up 99% of the time and the DC is up 99% of the time then the ACTUAL risk of BOTH being down is not 1% it is in real risk assenment and probability management something in the order of 0.01% of the time.
Now if the risk to your 50 man business is such that a 0.01% risk of failure will cost you MORE than the cost of installing, licensing and running an additional 2 domain controllers, then yes go ahead....
Tony GiangrecoCommented:
You can install a backup DC or RDC (Read Only DC) at each location. Its a bit of insurance that pays for itself the first time it's needed.
You have two choices: Install a second DC at each location or install a redundant WAN link.  Usually, the DC is only one of many services on the wrong side of the WAN connection. There isn't really a lot to be gained from having redundant DC's but not being able to access you key applications.

So unless the investment in the redundant WAN link is prohibitive for your location, that's what I would recommend.
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