Category Archives: Windows Server 2012 R2

Hyper-V UNMAP Does Work With SAN Snapshots And Checkpoints But Not Always As You First Expect

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Recently I was asked to take a look at why UNMAP was not working predictably  in a Windows Server 2012 R2 Hyper-V environment. No, this is not a horror story about bugs or bad storage solutions. Fortunately, once the horror option was of the table I had a pretty good idea what might be the cause.

San snapshots are in play

As it turned out everything was indeed working just fine. The unexpected behavior that made it seem that UNMAP wasn’t working well or at least at moments they didn’t expected it was caused by the SAN snapshots. Once you know how this works you’ll find that UNMAP does indeed work predictably.

Snapshots on SANs are used for automatic data tiering, data protection and various other use cases. As long as those snapshots live, and as such the data in them, UNMAP/Trim will not free up space on the SAN with thinly provisioned LUNs. This is logical, as the data is still stored on the SAN for those snapshots, hard deleting it form the VM or host has no impact on the storage the SAN uses until those snapshots are deleted or expire. Only what happens in the active portion is directly impacted.

An example

  • Take a VM with a dynamically expanding VHDX that’s empty and mapped to drive letter D. Note the file size of the VHDX and the space consumed on the thinly provisioned SAN LUN where it resides.
  • Create 30GB of data in that dynamically expanding  virtual hard disk of the virtual machine
  • Create a SAN snapshot
  • Shift + Delete that 30GB of data from the dynamically expanding virtual hard disk in the virtual machine. Watch the dynamically expanding VHDX  grow in size, just like the space consumed on the SAN
  • Run Optimize-Volume D –retrim to force UNMAP and watch the space consumed of the Size of the LUN on the SAN: it remains +/- the same.
  • Shut down the VM and look at the size of the dynamic VHDX file. It shrinks to the size before you copied the data into it.
  • Boot the VM again and copy 30GB of data to the dynamically expanding VHDX in the VM again.
  • See the size of the VHDX grow and notice that the space consumed on the SAN for that LUN goes up as well.
  • Shift + Delete that 30GB of data from the dynamically expanding  virtual hard disk in the virtual machine
  • Run Optimize-Volume D –retrim to force UNMAP and watch the space consumed of the Size of the LUN on the SAN: It drops, as the data you delete is in the active part of your LUN (the second 30GB you copied), but it will not drop any more than this as the data kept safe in the frozen snapshot of the LUN is remains there (the first 30GB you copied)
  • When you expire/delete that snapshot on the SAN  we’ll see the size on the thinly provisioned SAN LUN  drop to the initial size of this exercise.

I hope this example gave you some insights into the behavior

Conclusion

So people who have snapshot based automatic data tiering, data protection etc. active in their Hyper-V environment and don’t see any results at all should check those snapshot schedules & live times. When you take them into consideration you’ll see that UNMAP does work predictably, all be it in a “delayed” fashion Smile.

The same goes for Hyper-V checkpoints (formerly known as snapshots). When you create a checkpoint the VHDX is kept and you are writing to a avhdx (differencing disk) meaning that any UNMAP activity will only reflect on data in the active avhdx file and not in the “frozen” parent file.

Exchange 2010 SP3 Rollup 5 Added Support for Windows Server 2012 R2 Active Directory

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6 weeks ago (February 25th 2014) Microsoft finally took away the last barrier to upgrading some of our Windows Server 2012 Active Directory Environments to R2.  Most of them are still running Exchange 2010 SP3 and not Exchange 2013. The reason is that Exchange 2013 was not deployed is whole other discussion Eye rolling smile.

However that dis mean that until the release of  Exchange Server 2010 SP3 Update Rollup 5 last month we could not upgrade Active Directory to Windows Server 2012 R2. Rollup 5 brought us support for exactly that. We can now:

  • Support Domain Controllers running Windows Server 2012 R2
  • Raise the Active Directory Forest Function Level and Domain Functional Level to Windows Server 2012 R2

Please note that you cannot deploy Exchange Server 2010 (SP3 RU5) on Windows Server 2012 R2 and you’ll probably never will be able to do that. I’m not sure Microsoft has any plans for this.

Now our office moves have been concluded, meaning I can get back to IT Infrastructure instead of being an glorified logistics & facility peon, we’re doing the upgrade.

This also means we can move the Active Directory environments to the latest version so we have the best possible position for any future IT projects at very low risk. The environments are already at W2K12 functional level. If the budgets get so tight they lose/scrap EA or volume licensing it also allows them to run at this level for many years to come without causing any blocking issues.

The Hyper V Amigos Showcast Episode 2: Unmap

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We’re back for our second episode of the Hyper-V Amigos show cast. In this episode we discuss and demonstrate UNMAP in Windows Server 2012 R2 a bit. As always it was fun to work with Carsten Rachfahl.

2 Hyper-V Amigos having fun discussing UNMAP

 

Here’s our fun and unscripted (other than the PowerShell used in the demos) attempt at showing you UNMAP behavior with Hyper-V and a DELL Compellent SAN

If you want to read more on our experiences with UNMAP search my blog https://blog.workinghardinit.work/tag/unmap/. I have prepared some links for you.

I still need to get the slides uploaded, but all that info is in the blog posts.

Enjoy!

EDIT:

In relation to the question below about not much difference between Dynamically expanding VHD/VHDX. That demo didn’t work out so well here so I include  some screenshots of a comparison I just ran:

This is the dynamically expanding VHDX. on an IDE controller, no ODX.

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This is the dynamically expanding VHD on an vSCSI controller, with ODX.

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So yes, losing ODX makes things slower for dynamically expanding VHDX, but it still beats a Dynamically expanding VHD that has ODX.  A VHDX is a lot better at dynamically growing than a VHD.

Speaking At The ITPROceed Event–June 12th 2014, ALM Antwerp

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The Belgian IT Pro community is organizing the ITPROceed event a “technology geek fest” as they call it on their web site.

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It’s a joint venture between the IT pro community and Microsoft Belgium to help you all proceed in designing, deploying and operating Microsoft technologies.

The sessions will not only help you proceed but succeed as well. The speakers are Microsoft MVPs, MEET members & passionate community experts. They’ll share expertise & information gather by using these technologies in real life deployments.

A rich mix of technologies you have available and need today will be discussed like the Cloud OS, System Center, SQL, Office 365, Windows 8, Unified Communications, Lync, Azure and SharePoint.

I’m speaking

I’ll be speaking about the features in Windows Server 2012 R2 that make it “The Scalable & Capable Cloud OS”.

Come see how you can leverage the capabilities of Windows Server 2012 R2, a true cloud OS, to achieve powerful and scalable solutions. We’ll demonstrate how to use technologies as SMB Direct, DVMQ/vRSS, ODX, UNMAP, VHDX and Storage QoS. This will help you get the most out of commodity infrastructure and investment in Windows today.  We’ll share our experiences with you based on real life deployments to help you proceed and succeed.

Join us!

Really, make time in your schedule and attend this event by registering here.

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Attend the sessions, talk shop with your peers and discuss your questions with the experts. I’ll see you there.