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?

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    It's just wierd, I haven't heard a good answer to this one. Server 2003 R2 I understand - that was just a few new features that was easily installed on-top of existing 2003 installations. 2008 R2 is basically a new release, same difference as between Vista SP1 and Windows 7 - and it includes a lot of new ground-breaking features so... the name is just super-wierd to me. Commented Aug 19, 2009 at 10:44
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    Answered as a comment as I'm being cynical. Server 2003 and Server 2003 R2 will currently be retired at the same time. Had they have released Server 2003 R2 as 'Server 2006', then it would have had a longer lifecycle than it currently does. It offers people looking the latest and greatest with a 'new' product, at little cost for Microsoft, and as it won't get a longer support lifecycle than Server 2003. Just a money spinner for Microsoft? - I did say I was being cynical! support.microsoft.com/gp/lifepolicy.
    – user11604
    Commented Sep 14, 2009 at 7:01

9 Answers 9


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.

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    When I first saw 2003 R2 I didn't understand why I couldn't just 'install' it, because I thought it was like a service pack. Commented Aug 19, 2009 at 9:22
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    You actually can, by running the installer from the second CD-ROM on an existing Windows 2003 setup.
    – Massimo
    Commented Aug 19, 2009 at 9:46
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    Yes you can just install 2003 R2 BUT it is not a free upgrade, it's a new version that costs money (or needs a subscription or other upgrade advantage anyway)... which makes 2008 R2 EVEN MORE wierd as that is NOT just an upgrade... aaaargh it's freaking annoying ^^ Commented Aug 19, 2009 at 10:42
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    Mmmm, marketing! Commented Aug 19, 2009 at 11:43
  • Too many changes to call it SP2. Didn't want the "wait until SP1" of a "new" Server OS.
    – Chris S
    Commented May 21, 2010 at 13:33

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).

  • Can't it be both licensing and kernel changes? :)
    – osij2is
    Commented Sep 14, 2009 at 18:54
  • How can it be both? There were NO kernel changes in 2003. Commented Sep 14, 2009 at 23:11
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    I would also point out that R2 is 64-bit only, whilst 2008 is both 32-bit and 64-bit. Commented Dec 29, 2010 at 0:25

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.

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    Windows ME had an awful reception because it actually is the worst thing that ever came out of Microsoft...
    – Massimo
    Commented Aug 19, 2009 at 9:47
  • @Massimo, I wish I could up that comment 10 more times. So true
    – MDMarra
    Commented Aug 19, 2009 at 11:10
  • Worse than Clippy?
    – MartW
    Commented Oct 16, 2009 at 14:23
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    I thought it was generally acknowledged that this particular honour goes to Microsoft Bob. Commented Oct 16, 2009 at 14:26

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...


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).


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?

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    Yes as it includes stuff like Direct Access, branch cache and .NET support on Server Core. Then there's hyper-v 2.0 with live migration and various other enhancements, powershell 2 by default and the IDE/ui for it, boot from vhd which only Win7 and Server2008 R1 can do, and various business use case stuff... I can see the point in R2:ing it only if Win7 is also called Vista R2 ^^ IIS7.5 is the only thing actually worthy of R2ing as it's just a rollup of previously separately released features and fixes afaik but with so many vital new features the ambiguous version addressing confuses people. Commented Sep 14, 2009 at 6:41
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    What I mean is there's just too many new features that really need R2 and Windows 7 to work at all - and many people will want those features and Server 2008 won't do them unless it's a Server 2008 R2. It's confusing enough when adding the R2 in internet searches trying to separate the two different server versions and getting info for both :7 Commented Sep 14, 2009 at 6:43
  • I can understand your comment about confusing people. But I often forget Microsoft is always in a tough position with all of their products as their support for legacy versions and trying to add new features creates such product marketing confusion. Does R2 include new stuff? Yes. But so do some service packs. So, is a service pack a new version of Windows Server? Tough to say. I agree with you in the sense that the "R" labeling can be misleading or at the least doesn't fully describe how it fits in the family of products.
    – osij2is
    Commented Sep 14, 2009 at 6:59
  • Well, Windows 7 is considered a major release, and Server 2008 R2 inherit most of the Windows 7 changes and new features.
    – Yuhong Bao
    Commented Jul 24, 2012 at 4:46

"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.


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.

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    You have to spend for R2 versions anyway, your argument makes no sense. Commented Sep 14, 2009 at 20:26

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