I'm sure it is possible if you read up and test beforehand, personally I'd leave it alone though!
You should really have at least 2 domain controllers for each site. I would suggest doubling up on DNS and DHCP too. You should also be aware that if your Global Catalogue server goes down, Exchange will go down too so making both DC`s global catalogues is also a plan. on a network of this size, the replication traffic would be minimal so it wouldn`t hurt.
hyper-v does do high availability in the Active/Standy (A/S) sense using shared SAN storage, but that's really based on the new and improved cluster services engine in w2k8 and it's built-in fault tolerance capability rather than a specific vm HA product like Vmwares HA...hyper-v doesn't have live, uninterrupted VM mobility such as a vmotion-type implementation....but the mobility solution it does have should allow customers to migrate VM's to new hardware with a downtime of around 15 seconds before everything is back to an online state (the delay means it's 'quick migration' rather than 'live migration'). In some cases that's not acceptable, but many companies who'd like the cheapness of an out-of-the-box virtualization solution it's not a dealbreaker.
Leave virtual server for the training lab is my advice, and it doesn't sound unreasonable to me that a standy in any A/S clustering or HA solution should need to be licensed. It's common in certain parts of the commercial unix world (where you pay through the nose for such solutions for both clustering engine, application-specific extensions AND multipathing software) - why should MS be any different, they're already giving a ton of stuff away virtually for next-to-nothing depending on the type of agreement you utilise for purchase.
Last edited by torledo; 21st June 2008 at 12:10 AM.
It does take a while to do though, and you need to be sure that replication works between the two Exchange servers (don't use smarthosts in the config, you have to use SMTP connectors).
Yep, that's what we have - disk images are mirrored in real time, but not actual VM state. If a physical server went down we would have to boot up copies of the VMs on the backup server, so we don't have instant failover, it'd take us a few minutes to get back up. It's maybe something I'll look at in my Copious Free Time over the summer :-)'mirroring' is really a traditional clustered or HA solution where OS instances are installed on the machines in the cluster but one or more machines remain idle as in clustered Active-Standy
I don't think that would help us - we're not running VMs on top of Windows, we're running VMs on top of CentOS + Xen. I'd like to be able to simply pay for a copy of Windows Server 2008 that I can run in a virtual machine and move around as needed between physical machines. Fine if we need to pay a bit more than just for standard edition (maybe £150 for "VM Edition"?), but the current situation seems as though if you want any sort of live failover facility based entirely on Windows Server you have to buy datacentre edition for each processing machine, plus pay for whatever third-party stuff you need to get Windows to be able to mirror disk volumes accross a network or act as an iSCISI server if you're using a SAN. Microsoft are looking a bit behind the times here - also, how do you handle licensing pre-built VM images based on Windows?i agree that the live mobility should not be tied to physical machines but should be implemented based on unlimited virtualization rights as dmccoy described with datacenter edition.
Sorry, we're wandering off topic here - we'd better nip over to the virtual machines forum if we want to winge any more about Microsoft's overly-complex licensing issues!
if you require more than four instances do you then have to pay to license each additional instance of windows server 2008 running in a VM ?
Moving on to windows datacenter edition....windows datacenter is licensed per socket and allows you to install unlimited number of VM's that the machine can handle at no additional cost. Because it's licensed per socket, setting up a hypervisor on a four socket box has a high upfront cost because of the relatively high per processor price, but the value is in that you can install 5, 10, 15 whatever is technially feasible without paying any additional licensing cost beyond that initial single datacenter license purchase.
IF that's the case, datacenter is great value, and enterprise isn't a bad deal.
Even a HA solution, even though it means you're paying twice for the privildge of runing idle machine(s), it's still decent value i think.
However if you have to pay for each windows VM instance, then obviously it's not good value.
There is one solution - run Windows Datacentre on top of Xen, then run Windows VMs on top of Windows Datacentre. But that would just be silly...
So I have 2 big servers, 8 VMs on one. I have 2 enterprise licenses for it. Now, I can buy just one license for the second server, and I can migrate 4 VMs, but only those from *one* base license! Complicated isn't it! Tracking to stay *technically* within the exact license terms is nearly impossible.
Datacenter (academic) is much better value than it was, considering you could be licensing 2 sockets and have 8 cores! Mine are still dual socket, single cores
It also applies to things like Exchange, and other MS server products. This can vary though. I simply don't move my exchange box around much.
Virtualisation isn't a method of saving money as you know, but this is often forgotten after just looking at the savings on the number of physical boxes. It's just for consolidation and dynamic provisioning really, with some extra things thrown in.
Last edited by DMcCoy; 22nd June 2008 at 10:02 PM.
For MS Server licensing see this MS blog post.
Believe it or not, somewhere there's a video of a father explaining MS Server licensing to his 6 year old daughter with sweets. Can't find it now - I'll see if I can dig it out.
To get back to the original question: You should have no less than 2 DC's. The work involved in restoring AD when your one and only DC has a catastrophic failure doesn't bear thinking about. I know - I was in that position once. Since then I've always had 2 DCs.
Make both of them global catalogue servers. If the PDC emulator goes down, it's easy enough to make the other one seize roles, while you quickly build another server and make that another DC, bringing your total back to 2.
I think 2 would be enough for a school.
Last edited by OverWorked; 22nd June 2008 at 09:33 PM. Reason: added a bit more
...except that the blog post doesn't get around to answering that question. Hmm. Good point...[if that's the case do you need to request a VLK for each instance of the OS you plan to install for VM usage, even though you've not purchased those additional licenses?
Yes, pretty decent (especially at the academic pricing we get :-)). Really, we might as well get Enterprise or Datacenter, as it's kind of a buy-three-get-one-free deal by then.Even a HA solution, even though it means you're paying twice for the privildge of runing idle machine(s), it's still decent value i think.
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