I've searched, but I can't find anything that explains why Microsoft started labelling new versions of Windows Server (and now SQL Server) as R2 releases.
If they're new releases, why not simply give them new names?
Or is there something going on with upgrade pricing or licensing?
R2 is a licensing thing. It has nothing to do with kernel changes or service packs or other such things.
Remember 2003? And then 2003 R2? 2003 R2 did NOT have any kernel changes. 2003 R2 was basically a bunch of add-ons, SOME of which were freely available from Microsoft, some were not. It did introduce some new technologies/advanced some existing ones and bump the schema up a version, but the KERNEL was the same.
Server 2008 R2 is radically different from Server 2008. There are MANY kernel changes, especially in the area of power management (core parking for one) and the ability to handle (with the appropriate version) 256 Processor Cores.
R2 provides a way of saying "Your CALs are still good". With R2, you buy the SAME CALs (the CALs don't need to be upgraded) that you did with the original version.
(FYI, I saw a presentation on 2003 Server by a Microsoft Rep who challenged the thought that Windows 7 was Vista R2 and upon hitting him with the logic based on kernel similarities, he explained why R2 exists).
One guess: To remove the psychological barrier to upgrade. If you call it R2 then it looks like a Service Pack (which it is to some extent), whereas if you call it 2010 then it looks like a huge new version with massive incompatibilities, which will make people very reluctant to update.
I think it's a commercial move. Windows Server 2008R2 looks old if Microsoft releases a new version in the future. Let's say they'll release a Windows 2014, then Windows 2008 R2 looks like 6 years old (which isn't).
Because it is not a NEW version, it is really a tidying up of the old version. Basically think of it as too many underlying changes for a service pack but too few obvious features to be a whole new product.
They've done this before with things like Win 98SE. Compare the reception that got to Win ME.
You have to wonder if Windows XP SP2 would have been called "Windows XP R2" as it was a pretty big re-write of the Windows XP code.
On the server side, whatever Microsoft do someone will complain. I suppose it does make it clearer to people that their CALs are still good, but hopefully people making major decisions on network operating systems are going a bit further than the name of new products when making their decisions. At the end of the day a rose by any other name...
"Q: What does "R2" even mean? Is this really a new OS?
A: This means that while the operating system maintains the same codebase, it includes a lot of new features and functionality not present with the original release."
link: http://searchwindowsserver.techtarget.com/generic/0,295582,sid68_gci1391033,00.html
Could be for early adopters in MS technology. Many upgraded to 2008 right away, and needed functions of the R2 release when it was released. But did not want to change OS completely, hence the R2.
Also there is the common belief that you don't upgrade your MS OS till there is one published service pack, this helps the public see MS is actively working on providing features in an OS that were not there before ie listening to customer-base.
It's not a psychological thing at all. It's called R2 because it's a different kernel version (and build) from 2008. Server 2008 uses the 6.0 kernel (build 6001), 2008 R2 uses the 6.1 kernel (7600). See the chart on wikipedia.
R2 is a better way of describing it because the services packs don't change the kernel (to my knowledge) but R2 isn't exactly that much newer as a completely new version. The difference between Windows Server 2003 and 2008 are huge, but changing the kernel won't typically be obvious to users as it's an internal change within the OS. There's seldom real new tools, interfaces or features with an "Rn" label. It's just an upgraded core where as newer versions have newer core with additional feature and tools.
For Windows 2008 R2, according to wikipedia: "Version enhancements include new functionality for Active Directory, new Virtualization and Management features, the release of IIS 7.5, and support for up to 256 logical processors."
So IIS 7.5 and some new functions for AD/Hyper-V. Do you think that those additions worth the title Windows Server 2010?
I figure that calling it "R2" means that there are more changes than a service pack, but not enough noticeable new features that MS marketing thinks they can convince people to spend for a new version. But that is just my guess.
