I recently had to move a VM I created in Hyper-V 2012 to a 2008R2 Hyper-V server.

This is the process I followed as well as the problem I came across.

Created a new VM on the 2008R2 server.

Copied the 2 VHD files across.

Attached them and started the VM.

When the server started up there were 2 things I picked up that was not working. The disk Manager and the NIC. The NIC icon would just be stuck on spinning. How I resolved it was to shutdown the host server and add a second nic. Don’t remove the first one. When the server next booted up it installed the second nic and some how re-applied the config. I still had to wait about 15 min for everything to start working. Once this happen I connected the server to the physical network and did a final reboot.

Everything was working fine after that.

• You have 3 type of swap files – 1. Host swap file (4GB) 2. VM swap file (Size of memory that you allocated to the VM – Space consideration when plan your design) 3. Guest OS swap file.
• VM’s heavily rely on CPU cache – Get CPU’s with high L1/2/3 cache.
• You could purchase solid state disks for the partitions where your host will be installed and store the VM’s swap files on there – This will improve performance.
• If you don’t need to allocate additional vCPU to a VM then DONT – It will use extra memory overhead to run the VM’s (Rather assign an extra core if needed unless your app is configured to run with multi PROC).
• Optimize VM’s according to NUMA – Don’t allocate more RAM to the VM than what is on the physical RAM section per CPU.
• Plan 60% of resources for usage and 40% for maintenance and future growth.
• Make sure you have enough resources on all hosts that are part of your HA or fault tolerance cluster to accommodate for VM’s that might be moved to host in case of another host failure.
• Rather scale out than up for HA.
• Don’t put your management and IP storage on the same network.
• For HA implement redundancy heartbeat networks and redundant isolation addresses.
• If you are planning to enable fault tolerance on VM’s then only assign 1 vCPU to the VM. FT is not supported on more (This is on vSphere 5.1 and earlier).
• Dedicate networks for Fault Tolerance.

Below are some high level best practises for your vSphere environment:

• Remove your ISO images from your VM’s as soon as you are done with them – Don’t leave them connected.
• Remove all devices that you are not using on your VM’s (This prevents unnecessary Kernel processing).
• Isolate your iSCSI traffic, don’ use CHAP.
• Unmount datastores before you delete them.
• Set alarms on your critical datastores – Alerts you before it runs out of space (It will freeze the VM’s on the datastore should the datastore run out of space).
• Create VM templates.
• Enable CPU and Memory hot add on each VM (Not enable by default). Remember that the hot add is limited to the OS limitations – eg: Server 2003 does not support CPU hot add.
• Dedicate cores to VM’s – Don’t over commit.
• Change your block sizes according to application recommendations – eg: MS SQL uses 64k block sizes (So set this on SAN and guest OS level).
• Configure VM startup and shutdown – eg: DC start up first, DB servers second, Web/front end servers third and test/non-critical VM’s last. Remember to configure this on each host, if it vMotions the VM’s to another host the startup/shutdown settings will change according to what has been configured on that host.
• Configure IP hash as load balancing option – Need Link Aggregation support on switches (Switches needs to be stacked).
• Run HA and DRS together.
• Join vCenter and host to domain and let the ESXi administrators use their domain accounts to administer.