What is the difference between server 2008 R2 and server 2012?

Hyper-v in 2012 now allows live migration to and from NON clustered machines. in 2008 r2 they have to be clustered. This is a HUGE thing which is worth going right to 2012 for. For a small business anything hyper-v is good since it allows them to create a virtual server without having to pay for it.

It has other big features like changing dynamic memory while the machine is running when in 2008 r2 you have to stop the virtual machine .

IIf hyper-v will be used in the future I think starting with 2012 now is a good idea.

WIndows server 2008 R2 HyperV hard disk maximum capacity is 2 TB but for windows server 2012 Hyperv Hard disk maximum capacity is 6 TB.

Snapshot merging needs to be done in shutdown mode for windows server 2008 R2 but for windows server 2012 can be done online mode

Compare scale of Windows Server

Windows Server R2

Host  

Logical processors                         

Physical memory                        1 TB

Virtual processors per host         

Virtual Machine

Virtual processors per VM           GB

Virtual disk capacity                   2 TB

Active virtual machines               

Cluster

Nodes                                         

Virtual machines                       1,

Windows Server R2

Host  

Logical processors                        

Physical memory                         4  TB

Virtual processors per host          2,

Virtual Machine

Virtual processors per VM        1 TB

Virtual disk capacity                     TB

Active virtual machines               1,

Cluster

Nodes                                          

Virtual machines                        8,

Well, the biggest technical differences are that Windows Server 2012 can handle far more physical hardware than Windows Server 2008 R2. For example the supported logical processors were raised from 64 (2008) to 320 (2012), the RAM (from 1TB to 4TB) and virtual processors per host (512 to 2048) were quadrupled. In the version 2012 it also support now some new technologies like Dynamic access control, Active Directory virtualization support, Dynamic IP restrictions, multiserver management and so on. The number of new features is longer than I can manage to list here.

Some of the old features come in new versions, for example IIS is now in version 8, Power Shell in version 3, Hyper-V in version 3 and SMB also in version 3.

Furthermore, Server 2008 (regular version) came as 32 and 64 bit version, 2008 R2 started with migrating to a full 64 bit system and 2012 comes only as a complete 64 bit operating system which brings higher performance and capability of hardware support.

But it's not easy to give a detailed list because the IT has come a long way between those two editions and every single area has had improvements and changes. I listed only the biggest ones I got to know from my expertise fields in support and administration.

Difference between windows server 2008 R2 and windows server 2012, I will try to list the major difference and new features. 

IIS 8: Windows Server 2012 features IIS 8 which brings its latest version with features like script pre-compilation, granular process throttling, centralized certificate management, etc.

Power Shell 3.0: Power Shell is going to be the future of Microsoft. With Command line interfaces being less popular over the last decade, Microsoft is building up with newer versions of power shell with more advanced features.

Server Core: Server core was introduced in Windows Server 2008 as a competitor to Linux/Unix operating systems but with limited features. Microsoft is coming up with advanced features and with Server 2012 installation; it gives an option to switch to Server Core and vice-versa after the installation.

Direct Access: Direct Access was considered to be a replacement to VPN and was introduced with Windows Server 2008 but with Server 2012, it is much easier to use.

Hyper-V 3.0: Hyper-V introduces a new version 3.0 which offers an extensible virtual switch and live storage migration which is a step up from Server 2008 R2’s Quick Storage Migration to prevent downtime. It is also capable of migrating virtual machines (VMs) without shared storage.

SMB 3.0: SMB 3.0 provides improved performance of SMB Direct (SMB over RDMA), improved SMB event messages, helps Hyper-V live migration over SMB, and other new features which makes it a robust feature in Server 2012.