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Two Big SQL Server Availability Announcements from Microsoft

By: on November 7, 2019 in Azure, FCI, High Availability, Licensing, Shared Disk, SQL Server, SQL Server 2019

Hello everyone. I have not had much time to blog, but there are a few things that you should be aware of and that I have an opinion about. Both were recently announced – one before Ignite and PASS Summit and the other this week somewhat quietly in a session at Ignite.

Big Deal #1 – Azure Shared Disks for FCIs (and One More Thing …)

If you have ever heard me present, you will know I am not the biggest fan of deploying Always On Failover Cluster Instances (FCIs) in non-physical environments. That includes in any of the public clouds. Why? There are quite a few reasons which I will not go into here, but I will discuss the biggest one: shared storage. Configuring shared storage is awful in any of the public clouds. Sure, if you use something like VMware’s solutions in any of the public clouds you can take advantage of vSAN, but that will not work for most folks. I’ve been VERY vocal how much the Storage Spaces Direct solution is currently a fairly terrible experience at least in Azure. SIOS DataKeeper is a good solution, but for some, they do not want to purchase anything else; they want a workable, native solution. Sure, you can use iSCSI but why would you?

You get the idea. It kinda sucks right now (forget the fact you probably should not be doing it to begin with). I’ve had conversations with both the SQL Server and Windows Server dev teams about this. They know my displeasure.

Maybe they finally heard me. At Ignite during BRK3253 – Windows Server on Azure overview: Lift-and-shift migrations for enterprise workloads (man, I hate how MS does not capitalize titles ….), Elden Christensen and Rob Hindman from the Windows Server dev team (both of whom I know very well) announced the private preview of Azure Shared Disks (it’s apparently being renamed, and isn’t Shared Azure Disks) and show a non-SQL Server-based demo. If you want to skip ahead, they talk about it at 22:34. This will not change my opinion on using FCIs up in Azure, but it will sure as heck make it easier to deploy. As soon as I can test, I’ll report back. There is another session BRK3283 Optimize price-performance and lower TCO for your workloads with the next-gen Azure Disks (not live as of this posting) which will cover more of the Azure disk stuff.

One more recent change which I will be most likely showing and talking about for the first time in a few weeks at my SQL Server LIVE! precon is the ability to use Azure Files for FCIs.

I would recommend you also have a look at the Ignite sessions from John Marlin to see and hear about anything new coming in WSFCs in Windows Server vNext LTSC. The biggest announcement I’m aware of that could affect SQL Server (and specifically FCIs) is the ability to stretch a WSFC with Storage Spaces Direct (S2D). THR2155 I can’t currently watch (network error on the Ignite site), so I haven’t been able to ascertain what else could impact SQL Server. If there’s something else, I’ll either update this post or do a new one if it’s really major.

Big Deal #2 – Changes to Licensing for Availability Scenarios

On October 30th, Microsoft let the cat out of the bag that licensing rules for the availability scenarios were changing as of November 1, 2019 if you have Software Assurance (SA). We always tell our customers that SA is often worth it. You can see the full new rules in the SQL Server 2019 licensing guide. The rules apply to all supported versions of SQL Server.

Let that sink in: supported versions of SQL Server. What does that mean? For example, if you are using SQL Server 2016 with Service Pack 1 whose support ended on July 9, 2019, you would need to go to Service Pack 2 or later. Microsoft is not going to come in and crash your party, but if they audit you or you are going through a true-up for licensing, it could bite you. This means you need to stay current to take advantage of these benefits.

I’m going to discuss what I feel are the biggest game changers. I knew licensing was changing as I had conversations with Microsoft around this months ago. I was not sure what the final result was going to be, but I’m fairly pleased. Is it perfect? No, but it’s much better than it was.

It’s interesting to note that for licensing purposes, Microsoft defines HA as a synchronous replica with automatic failover and D/R as an asynchronous replica with manual failover.

Change #1 – Backups and DBCC on a Secondary Replica Is Now Free

I still hate the use of the words active and passive, but that’s a whole other blog post. In talking with Microsoft, there are other reasons some of these terms are used, but again, irrelevant at the moment. Taking terminology out of the picture, with SA, you can now generate full, copy only backups, transaction log backups, and run DBCC on a secondary replica of an AG without incurring a license. That of course assumes no other databases are live on that instance. That is a huge change because through SQL Server 2017, those were considered “use” and you had to license. This is one thing that should have been there since day one, but I’m just glad they finally corrected their stance.

Change #2 – Allowance for Disaster Recovery Testing

This one is buried in the licensing document, but very big. Here’s what it says:

Customer may also run primary and the corresponding disaster recovery replicas simultaneously for brief periods of disaster recovery testing every 90 days.

I can’t emphasize how huge this is. For example, there was always a question if you were using something like VMware’s Site Recovery Manager (SRM) as your primary D/R method. Now that is covered in pretty clear language. Thank you, Microsoft.

Change #3 – Disaster Recovery Is Now Covered (To a Point …)

Prior to these changes, you only got one “free” replica. If you had an AG with three replicas, two local for HA and one remote for D/R, you paid for two of those. With this licensing change, both the HA and D/R replicas would be covered if you have SA. This is huge.

Change #4 – Azure Disaster Recovery Replicas Are Covered via the Azure Hybrid Benefit

This is related to #3. I’m sure this one will irk some, and if so, please comment below. I know Microsoft is listening 🙂 If Azure is your cloud provider and you want to stick a replica for your AG up in the cloud that is just for disaster recovery, you are now covered with SA. This was not the case before. This new benefit does not apply if you are using Amazon Web Service or Google Cloud.

With this benefit, you can technically have up to three passive replicas (one on premises for HA, one one premises for D/R, and one up in Azure for D/R). Anything else would still seemingly need to be paid for. So if you have two D/R replicas in different data centers (for example, your main data center is in Boston, and you have D/R replicas in London and Chicago), you are going to pay for one of those. That is still better than paying for two.

Things That Could Use Clarification

Due to the “standardization” of terminology, FCIs, AGs, and log shipping are basically treated the same in this document. That’s confusing. Microsoft says this:

Each of these implementations uses different terminology. The examples that follow use ‘Active’ as the read-write database or instance (also referred to as Primary Replica in an Always On Availability Group) and ‘Passive’ for the write only database or instance (marked to not-read, referred to as Secondary Replica in an Always On Availability Group).

But that’s not the terms we use for FCIs in technical documentation. For example, FCIs do not have “write only instances”. You install the binaries on other nodes of a Pacemaker cluster or WSFC and then the FCI can fail over to it. It’s not a “live” instance. I know this is probably not changing because documents like this go through legal reviews and has to match other similar documents/licensing terms for things like Windows, but it irks me to no end.

Also, I am wondering how all of this affects distributed availability groups and how the forwarder is considered. Is it passive or active from a licensing perspective? I’m hoping they clarify that.


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