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Overcoming Performance Issues With SQL Server Alwayson Availability Groups

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Asynchronous vs synchronous replication on AlwaysOn

From attending the sessions at PASS Summit this week, it has become obvious that AlwaysOn is a hot topic with about six sessions dedicated to this solution . The one thing that I learned is that although the solution certainly has its applications, most of the successful deployments are based on using AlwaysOn in an asynchronous fashion. The reason people avoid the synchronous replication option is that the overhead is too great. During synchronous replication any write must be committed on the replica before it is committed on the source. In the testing that I have done, this overhead introduced can be as much as 68%.

For example, in a test where I have a database inserting about 1,000,000 rows per second and we measure the throughput on the log file, we see that with no mirroring in place we are writing about 400 MBps. Once we start replicating that database with AlwaysOn Availability Groups across a 10 Gbps LAN, we see about a 68% drop off in performance, with this particular database slowing down to about 250,000 inserts per second.

Asynchronous vs synchronous replication on AlwaysOn
Figure 1 – MBps written to a SQL Server database before and after AlwaysOn Synchronous Mirroring

If you are considering the solution as a replacement to your failover cluster, this drop off should be of a major concern to you. In order to achieve the automatic failover that you are accustomed to in failover clustering, you must use synchronous mirroring, which means that you must live with this performance hit. Generally this is not going to be acceptable, which is probably why you don’t hear the experts recommending such configurations on a regular basis.

So what should you do?

Should you stick with you traditional failover cluster and a SAN? What if you want to take advantage of fast, high speed storage such as Fusion-io? In that case, you can’t use a traditional cluster…or can you?

The good news is that you can build a cluster without a SAN and do it all without the expense, limitations and overhead associate with AlwaysOn Availability Groups (more on the limitations and expense in my next blog post). By using DataKeeper Cluster Edition you can build clusters without shared storage AND the overhead associated with Synchronous replication is closer to 10% vs. the close to 70% we see with AlwaysOn Availability Groups.

Come to booth 351 at #SQLPASS and I’ll be glad to demonstrate how the solution works.

Reproduced with permission from https://clusteringformeremortals.com/2012/11/09/how-to-overcome-the-performance-problems-with-sql-server-alwayson-availability-groups-sqlpass/

Hurricane Sandy Disaster Recovery For Business

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The accident taught us the importance of Disaster Recovery. Have you prepared well for it?

My thoughts and prayers go out to those affect by this massive storm. Although I live in NJ, my neighborhood remained relatively unscathed other than some downed trees and power lines. The pictures coming in from the coastal communities up and down the eastern seaboard show that many people did not fare as well. I’m hopeful that most of the damage is property that can be rebuilt, but I am sorry to hear that some people lost their lives and I can only imagine the pain of their friends and family – I am truly sorry for their loss.

Need help with Disaster Recovery?

As an employee of a company that specializes in disaster recovery software, I am also privy to many stories of companies that lost data that cannot be replaced. Many of these companies never recover from such catastrophes, but those that do are usually the ones who immediately look to put into place a plan that includes some sort of real-time data protection that includes replicating their critical data offsite or to some cloud repository so they are never caught in such a predicament again. If that is your story or even if you were lucky enough to avoid disaster this time but want to prepare ahead, please contact me immediately so I can help you assess your risks and recommend some data protection and DR solutions to help mitigate the risks.

Reproduced with permission from https://clusteringformeremortals.com/2012/10/30/hurricane-sandy-disaster-recovery-for-business/

Achieving High Performance And High Availability For SQL Server

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Register here to learn how high performance and high availability for Microsoft SQL Server can be achieved with solutions from Fusion-io and SIOS. This powerful combination delivers high-speed storage and high availability for SQL Server without the limitations of single copy clusters or AlwaysOn Availability Groups.

Make the switch and enjoy:

  • Cost savings
  • Higher database performance
  • Smaller floor space requirements
  • Lower cooling and power demands

… all without sacrificing availability.

The end result: faster performance at a fraction of the cost of a typical SAN with 100% data availability.

Ready to learn about how Fusion-io and SIOS could achieve better results with Microsoft SQL Server. Hear from our featured Speakers:

Dave Bermingham is recognized within the technology community as a high availability expert and has been a Microsoft MVP in Clustering for the past three years. David’s work as Sr. Technical Evangelist at SIOS has him focused on delivering high availability and disaster recovery solutions. David holds numerous technical certifications and has over twenty years of technology experience focused on application availability.

Jamila Gunawardena is a Senior OEM Sales Engineer for Fusion-io. Jamila has over 15 years experience in Software Engineering and System Design with expertise in Internet, Bioinformatics, and Semiconductor DFM solutions. Currently, Jamila is focused on ISV and appliance partnerships at Fusion-io.

Geoff Hiten is a Microsoft SQL MVP and is currently an Infrastructure Architect for Intellinet. Geoff began working with SQL Server in 1992 with version 4.2 and has used every version since. He specializes in high-availability and high-performance SQL systems. Geoff is heavily involved in the Microsoft SQL Server Community and was initially awarded MVP status in 2004. Geoff was appointed in 2011 to fill an interim Director position at the National PASS organization.

Reproduced with permission from https://clusteringformeremortals.com/2012/09/12/achieving-high-performance-and-high-availability-for-sql-server/

Need Alternatives to AlwaysOn Availability Groups, Try SIOS DataKeeper

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Looking For Alternatives to AlwaysOn Availability Groups?

Microsoft made announcements about its most widely anticipated availability options that is being introduced with SQL Server 2012. This changes include AlwaysOn Availability Groups which will only be available with the Enterprise Edition of SQL. The cost of SQL Server Enterprise is $27,496 for any server (that has up to 4 physical processors) vs. $7,172 for Standard Edition. To take advantage of “Read-Only” replica, the cost of the solution is doubled ($54,992) since you have to license both the source and the target server. With such a high price point, you begin to wonder if there are Alternatives to AlwaysOn Availability Groups. Keep reading. Because I’m going to introduce SteelEye DataKeeper Cluster Edition which probably gives you the best bang for your buck.

The good news is that Microsoft still allows you to build 2-node clusters using SQL Server Standard Edition. Since this is generally deployed in an active-passive configuration, you do not have to license the standby server. So for $7,172 you can build a pretty robust 2-node SQL cluster. That’s assuming you have an enterprise class SAN that you can use to store your cluster data.

What’s that you say, you don’t have a SAN? Or you’d rather build a solution that eliminates the SAN as a single point of failure. And instead allows you to use data replication to keep the data in sync between cluster nodes the way that AlwaysOn Availability Groups allows you to? Or perhaps you want to use take advantage of the speed offered by local attached SSD drives such as those offered by Fusion-IO, but yet don’t want to give up on availability?

The Greatness of SteelEye DataKeeper Cluster Edition

For the cost of a single copy of SQL Server 2012 Standard Edition and the very affordable addition of SteelEye DataKeeper Cluster Edition, you’ll be able to deploy 2-node SQL Server 2012 Standard Edition clusters with data replication. Best part? It’s about half the cost of a 2-node SQL Server Enterprise Edition AlwaysOn Availability Group. Furthermore, it’s about ¼ of the price of a AlwaysOn Availability Group with read-only targets.

If you find yourself answering yes to any of the following questions. Then perhaps, it’s a sign to seek Alternatives to AlwaysOn Availability Groups. Windows Server Failover Clustering and DataKeeper Cluster Edition may be a wiser choice.

  • Am I concerned about the cost of SQL Server Enterprise Edition?
  • Do I use replication or log shipping?
  • Do I need to support Lync Server or other applications that use distributed transactions?
  • Do I need to ensure that SQL Agent jobs such as database backups, optimizations, DTS and others continue to run regardless of the node in service?
  • Do I need to ensure that SQL login accounts are kept in sync between cluster nodes?
  • Do I want to minimize my administrative burden?

We’ve Done The Comparison

The following chart summarizes your SQL Server 2012 availability options. We’ve included the 3rd option which is to build a traditional SQL cluster using Windows Server Failover Clustering with DataKeeper Cluster Edition.

SQL Server 2012 availability options including Datakeeper

Failover Clustering with DataKeeper Cluster Edition is going to save you plenty of money. And, it also is going to help you overcome some of the inherent limitations of AlwaysOn Availability Groups.

About the only thing you can’t do with the DataKeeper solution is to have read-only targets. As I mentioned earlier, read-only targets requires a second SQL license, so to have that feature will cost you minimally $54,938. If you really must have read-only targets, you’ll be glad to know that you can mix AlwaysOn Failover Clusters with DataKeeper and AlwaysOn Availability Groups. Basically you would wind up with a 2-node SQL failover cluster with DataKeeper and a single standalone SQL Server acting as a read-only target for an AlwaysOn Availability Group. In that case, you would still need two copies of SQL Server Enterprise Edition – one for the cluster and one for the read-only target.

Essentially, do check out possible Alternatives to AlwaysOn Availability Groups to save costs and improve work processes. I demonstrated this solution at Tech-Ed 2011 in Atlanta last year and got a lot of really positive feedback. This particular demonstration shows a 2-node multisite cluster. However, fret not the same concept can be applied to single site clusters.

https://clusteringformeremortals.com/2011/05/15/sql-server-denali-hadron-multisite-cross-subnet-failover-video-demonstration/

Reproduced with permission from https://clusteringformeremortals.com/2012/04/05/sql-server-2012-standard-edition-availability-options/

Hyper-V Replica Coming In Windows Server “Next”

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Watch new feature Hyper-V Replica

Here is an interesting video that demonstrates “Hyper-V Replica”, a new feature coming in the next version of Windows. Skip to the 39 minute mark to see the demonstration.

http://digitalwpc.com/Videos/AllVideos/Permalink/3cb3788c-5c47-4b9e-987c-0dec4194058b/#fbid=slfi0dmNMqP

It looks like a very welcome feature that certainly will make Hyper-V even more competitive when comparing the feature set vs. price between vSphere and Hyper-V, especially with the new pricing announced by VMware.

I’ll be very curious to see if this integrates with Windows Server Failover Clustering to allow you create shared nothing clusters as you can today with 3rd party replication software, which I’ve demonstrated using SteelEye DataKeeper Cluster Edition in an earlier blog post.

Reproduced with permission from https://clusteringformeremortals.com/2011/07/21/hyper-v-replica-coming-in-windows-server-%E2%80%9Cnext%E2%80%9D/