We are currently migrating our old 2003 physical servers to a hyper-v based virtualization platform (hyper-v failover cluster with two physical machines) "HyperMain". We have also a separat Hyper-V environment on a single machine "HyperExtra". Today, our setup looks something like this (all win 2003): srv1: file server Srv2: DC1(+DNS & DHCP) srv3: DC2 (+DNS & DHCP) srv4: WSUS + AV server srv5: Exchange 2010 srv6: Log collection application server (MySQL) srv7: Very small Sharepoint 2007 installation for system administrative information srv8: Sharepoint 2003 for approx 100 users. srv9: Backup server srv10: Standard IIS web server Should we keep this setup (i.e. 10 virtual machines), go with "one service per (virtual) machine" or try to reduce the number of virtual machines? I guess the total capacity need will increase with the number of virtual machines. This is a small environment which seldom have more than 20 active users at a time.

It's mostly a matter of budget, as each vm depending on the os edition used on the host might take another license. seperating the roles on dedicated vm's is kinda "best practice", you rule out interference and have the highesdt flexibility with maintenance, so if you can afford the resources/licenses, id go with a role per vm. work for maintaining might be a bit higher with more vms (eg patching), but imo, the downtime you save as you can maintain selective with less impact on the users more than compesnates that. keep in mind that your backup machine most likely isnt a machine you can virtualize (assuming it backups to tape and as such needs eg a scsi or sas controller), unless its a backup to disk solution or somethinhg like that

Thanks, good advice! Since we already have Datacenter licenses I guess it leans towards one role per VM. That would give us around 10 VM:s on the main Hyper-V cluster which is hosted on two server blades each having two Quad Core CPU:s (Intel Xeon 5500). That would mean 5 VM:s per host in normal, but 10 on one in a failover scenario. Do you think that would be a problem? Regarding backup, we are planning to use a separate iSCSI with a disk array box. Would that be feasible with a virtual backup machine?

with data center, id certainly go with one role per vm (assuming the ram in the hosts allows it). with 20 (active) users, i think you will be good with the ratio, the most likely bottleneck would be io, and that would be the case with a shared iscsi no matter if its 1 or 2 hosts generating the bandwith vs the iscsi targets. you can perfmon your exisiting machines to get an idea of the resource usage atm. there used to be a recommendation to have max 8 vcpu's per core with windows 2008 r2 ()which i think got raised with sp1), but thats more of a guideline imo. in the end, your workload defines how many vm's you can have per proc/core. with backup to disk, a vm should work. the problem when backing up to tape is that you cannot assign the physical controller to the vm, so the vm wouldnt see the tape drives.

Great advice and reasoning, thanks!