Adding a physical DC

[DavR]

A systems design question for you on a Friday afternoon....

 

Our blade enclosure failed this week, which took down all of our VMs. We have redundancy in that the VMs are split over two servers in the enclosure, RAID on every disk etc, but the enclosure itself was a single point of failure. We're back up now after a hairy few days, but I'm wondering how best to avoid that single point of failure in future.

 

I'm considering installing a physical DC, that would also have DHCP failover.

 

The question is, whether to buy a new box for it, or whether I can just add those roles to an existing server. I have one physical server running Server 2012 R2, just for hosting backups right now.

 

Now, I'm sure I considered doing this once before, but held back for reasons I don't remember. Is there any reason why I shouldn't install those roles on the backup host server? Can anyone recommend a micro server box to just run as a physical DC?

 

Thanks in advance!

[ChrisC]

We have a DC hosted on our backup server on the other side of our site. This also means we have hyper-v manager on the backup server providing us a platform to restore critical VMs (using instant recovery) from VEEAM if our cluster falls over.

 

*extra info*

To get around backing that DC up in veeam because it's not in the cluster, we just do a WSB job for it onto a server that does get backed up.

 

Chris

Edited June 28, 2019 by ChrisC

[Linfit]

Can't see any reason not to use your existing box.

We have a similar situation in that all our VM's are on a Dell VRTX and the the chassis is a single point of failure, although it has two power supplies.

I fitted a Dell R230 server, in another cabinet and set this up as a DC/DHCP and it works fine.

We use proper DHCP failover/load balancing though, not just split ranges, and I think that needs a newer server version that 2012 ? So if you wanted to do that you might need to upgrade.

[Primus]

2012 r2 supports DHCP failover - 2012 or later supports it.

[supportman]

We have a 2nd server room with a full Hyper-V infrastructure that is unused, Backup server and 2nd DC.

 

Having a single point of failure is a very bad idea, whether that's a SAN, Blade enclosure or RAID on a single storage box.

[ChrisC]

We have a 2nd server room with a full Hyper-V infrastructure that is unused, Backup server and 2nd DC.

 

Having a single point of failure is a very bad idea, whether that's a SAN, Blade enclosure or RAID on a single storage box.

 

That's obviously the ideal setup if budget allows!

 

Chris

Edited June 28, 2019 by ChrisC
typo

[Oaktech]

I've got an HP microserver with 8GB ram and a 60gb SSD in a cupboard doing just fine. DC'ing is not a stressful role.

[DavR]

Can't see any reason not to use your existing box.

We have a similar situation in that all our VM's are on a Dell VRTX and the the chassis is a single point of failure, although it has two power supplies.

I fitted a Dell R230 server, in another cabinet and set this up as a DC/DHCP and it works fine.

We use proper DHCP failover/load balancing though, not just split ranges, and I think that needs a newer server version that 2012 ? So if you wanted to do that you might need to upgrade.

 

That was our exact situation in fact. We have a Dell VRTX, and the CMC card died. Restarted to try and recover it..... and the f***er wouldn't start up without it.

 

As others have said 2012 R2 does full failover, we already have that working on two other DCs, this would be adding a third.

[DavR]

We have a DC hosted on our backup server on the other side of our site. This also means we have hyper-v manager on the backup server providing us a platform to restore critical VMs (using instant recovery) from VEEAM if our cluster falls over.

 

*extra info*

To get around backing that DC up in veeam because it's not in the cluster, we just do a WSB job for it onto a server that does get backed up.

 

Chris

 

You see, now if I was starting from scratch, I guess this is what I'd do. Set up the other physical server as a VM host (we're using VMWare but principal is the same), and then run a backup DC and the backup host server on it.

 

I'm not killing off a working server if I don't have to though, plus that would mean additional licensing costs.

Edited June 28, 2019 by DavR

[ChrisC]

So guessing to avoid the cost of VMware licensing (having no idea how much that is and also if the role/tools can be added retrospectively without affecting the current server) a physical box where your backup server is located would be your best bet? As Oaktech mentioned, DCs don't require mega specs.

[DavR]

Well, if you were doing is correctly, you'd wipe the backup server and install it with ESXi OS, then add a VM for DC, and a VM for backup storage. Thinking about it, you'd probably need a hypervisor VM as well..... and Datacentre rather than Standard server licensing.... all of which I don't currently have the skillset for honestly.

 

The more I dance around it, I think I'm just going to install the DC/DHCP roles on my existing backup storage server. Backups take no processing power during the day, and DCs take very little overnight when no-one's on the system, balances quite well actually!

[jmak]

You see, now if I was starting from scratch, I guess this is what I'd do. Set up the other physical server as a VM host (we're using VMWare but principal is the same), and then run a backup DC and the backup host server on it.

 

I'm not killing off a working server if I don't have to though, plus that would mean additional licensing costs.

If you use hyper v as your hypervisor you get 2 guests and a hypervisor with a single server standard licence (you aren't allowed to use/install any additional roles on the host but you can install a full version of Server with a GUI to run the hypervisor). Probably doesn't make sense if you're a VMware house, but straightforward enough.

 

You could P2V the existing backup server and then just add it as a guest. When I first virtualized our server I used P2V and then ran it from hyper manager on my laptop; slow as a slow thing, but proved I had a working server before I flattened the physical server to convert it to a host.

 

As a halfway house, you could add the hyper v role to your existing backup server and then build a DC as a guest. It'd give slightly better separation of roles and would still have no extra licensing cost. You'd also be able to move it to a different host more easily if the need arose.

[DavR]

If you use hyper v as your hypervisor you get 2 guests and a hypervisor with a single server standard licence (you aren't allowed to use/install any additional roles on the host but you can install a full version of Server with a GUI to run the hypervisor).

 

Oh really? So I could run the hypervisor host, 1 x DC and 1 x Backup server, on one Server Standard license.

 

Actually now you put it like that, this could work, and it's a little more elegant than just bashing the roles onto an existing physical host.

 

The main hosts are running VMWare, but I'm not necessarily tied to WMWare, so this would give me a chance to evaluate Hyper V.... maybe I will trash the existing server and play with Hyper V over the holidays.

 

Thanks for the tips so far everyone!

[jmak]

From the ms document:

 

https://www.google.com/url?sa=t&source=web&rct=j&url=http://download.microsoft.com/download/e/6/4/e64f72bf-55e9-4d85-9efe-39605d7ce272/windowsserver2016-licensing-guide.pdf&ved=2ahUKEwicy6iJ3IzjAhWVr3EKHS9FC0EQFjAAegQIBxAC&usg=AOvVaw18AKSA5OcZFRAO-s-96tMO

 

1 Windows Server Standard edition permits use of one running instance of the server software in the physical OSE on the

licensed server (in addition to two virtual OSEs), if the physical OSE is used solely to host and manage the virtual OSEs.[/Quote]

[markwilfan]

Oh really? So I could run the hypervisor host, 1 x DC and 1 x Backup server, on one Server Standard license.

 

Actually now you put it like that, this could work, and it's a little more elegant than just bashing the roles onto an existing physical host.

 

The main hosts are running VMWare, but I'm not necessarily tied to WMWare, so this would give me a chance to evaluate Hyper V.... maybe I will trash the existing server and play with Hyper V over the holidays.

 

Thanks for the tips so far everyone!

That's exactly what I do. 3rd DC on this hyper v host running alongside a dpm VM in our backup server room

[southhamster]

We are looking at this too. Left field suggestion is to use one of our NAS which can host VM's. The QNAP we have can also DNS and DHCP natively too. Might get us out of a hole if our main server dies.