Hyper V host runs slowly when physical DC boots up before the guest VM DC

Alright, I have an odd problem I am facing.  First I have a mixture of physical and virtual servers, the virtual hosts run Hyper V.  All of the OS's are Server 2008 R2.  We have an issue where, after say, a power failure, the Hyper V host runs poorly. There are two server 2008 r2 servers on the network, both are DNS servers, and if you power down all of the servers and just let the Hypver-V host boot first, there seems to be no issue.  If the domain controller that is physical boots up before the Hyper-V guest does, then all hell breaks loose and the Hyper V host runs so slow that it is barely usable.  We have set the DNS server settings on the NIC to point to the physical DNS server first, then to the DC that the Hyper-V server is hosting second thinking that the host was having issues finding resources on the network, this did not seem to solve the issue.  So in short, when the Hyper V host is booted all by itself first, no issues, if the physical DC comes up first, hell breaks loose.  I checked the event viewer and did not find any DNS related events, so I am a bit stumped.  I know this is kind of a complicated issue so if you have further questions please let me know, thanks!
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Lionel MMSmall Business IT ConsultantCommented:
ok so you have a physical server that run a DNS and if you start it first then it causes a virtual server with DNS to run slow (or does it cause the Hyper-V physical server to run slow)?

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From my feeling of your description:
DNS settings are not "load balanced" and it looks like, this is the base of the issue....
If a client machine (DNS client) starts, it first tries to connect to the first DNS in the list. If the DNS is dead, it tries the second one.
If the DNS is there, but the DC is still in boot process, the client machine stays on this DNS and the performance maybe  poor during the boot process of the DNS server, as DNS responses maybe slow. So the client waits for the response. Also timeouts are possible.
If the server is completely booted everything should be fine. If the client machine is still slow even the DNS server is completely booted, then I would rather search for network issues. You may check on the client machine via NSLookup, which DNS server responds and maybe you find out, that performance is poor if the client ask one special DC machine, while it is fast if the client takes another one.
If this is the case, you may check the throughput between the virtual machine, the HyperV host against the slow DNS server if there is a performance problem.
Sometimes newer NIC drivers solve such problems.
Sometimes also a good idea just to change the ports of the switch. Maybe there is a switch port which makes trouble.

From the base construction, you should make sure, that a DNS client always contacts the fastest DNS first. Usually the virtual DNS may be the fastest ones (if the HyperV host is not overloaded) due to the 10GB connection between them.
I usually connect only the HyperV hosts itself as well as the DC on this HyperV host to a different DNS (other HyperVHost or physical machine. All other virtual machines connect to a DC / DNS on the same host machine.  
But also a physical DC / DNS for all machines should not a problem as long as the physical NIC of the HyperV host is not overloaded and the machine is not really poor equipped.
thinkconnectedAuthor Commented:
Thank you for your comments, to answer lionelmm,yes if the physical DNS server is booted first, the Hyper-V server runs poorly.  The Hyper-V server runs to guests, a Domain Controller / file and print server, and the Exchange server.  The DNS on the Hyper-V server is currently configured to point to the Physical Domain Controller, which is also a DNS server, first for DNS, then to the Domain controller it hosts, second.  Let me now if you have any other questions, this one has me stumped.
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Lionel MMSmall Business IT ConsultantCommented:
OK so which DNS is the primary DNS in your domain--the physical or the Hyper-V? I would expect if Hyper-V is the Primary DNS that all other systems would take longer to get ready for logging on as they are trying to reach the primary DNS that is not on.
thinkconnectedAuthor Commented:
The primary DNS server on the Hyper-V server is the physical machine because it boots faster and is up and running before Hyper -V host and guest OS's are.
Lionel MMSmall Business IT ConsultantCommented:
I suggest you "request attention" to your question as I can't be of any further help to you on this, so sorry.
thinkconnectedAuthor Commented:
No worries, its a tough one, never have seen this problem in my IT career.
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