SIOS SANless clusters

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Sacrifice High Availability For High Performance?

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Mosey on over to the Fusion-io website and read my guest post in their blog, Do You Have to Sacrifice High Availability for High Performance?

Invitation to join our Webinar

After you are done there, view the joint SIOS and Fusion-io webinar “SQL Server 2008 – High Performance and High Availability Through Fusion-io and SIOS”. Part of this webinar includes some VERY interesting benchmark information…you won’t want to miss it!

Reproduced with permission from https://clusteringformeremortals.com/2011/08/23/do-you-have-to-sacrifice-high-availability-for-high-performance/

SQL Server Denali And Hadron

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Microsoft’s latest version of SQL, code named Denali, is currently in CTP. One of the most anticipated feature is something called HADRON. Basically, it is has been described as mirroring 2.0. The best features of HADRON as I can see compared to mirroring as it is in 2005/2008 are as follows:

  • You can query the mirror (now known as a replica)
  • You can have more than one replica
  • Database are grouped into availability groups to ensure related databases always fail over together
  • Support for replicating more than 10 databases

If you want a great preview, check out fellow MVP Brent Ozar’s post, SQL Server Denali Rocks!

From reading Brent’s post I gather Microsoft only plans to include this in the Enterprise version of SQL. That is too bad for the many customers running SQL Server Standard as traditionally there is a significant price jump to go from Standard to Enterprise. However, that is good news for the 3rd party replication vendors out there who are providing similar functionality today on SQL 2005/2008 on Standard and Enterprise Editions.

SteelEye DataKeeper Cluster Edition for SQL Server

While it is not an exact duplicate of HADRON, a multi-site cluster using SteelEye DataKeeper Cluster Edition for SQL Server gives you a great solution for HA/DR without requiring shared storage. So while we wait for Denali and all the application vendors to start supporting Denali you might want to have a look at what SteelEye DataKeeper Cluster Edition can do for you today!

Reproduced with permission from https://clusteringformeremortals.com/2010/12/10/sql-server-denali-and-hadron/

Minimize Downtime Using High Availability Clustering And Data Replication For Sap

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Why implement high-availability cluster configuration?

What does it cost your business when your SAP system is down due to a hardware failure, an administrator mistake or for maintenance activities?  The impact can range from thousands of dollars lost in sales per minute to significant drops in employee productivity and customer satisfaction.  Through the implementation of a high-availability cluster configuration, downtime from both planned and unplanned outages can be virtually eliminated.

SteelEye and SAP AG have worked closely together to ensure that the availability needs which corporate users have for critical business infrastructure running on Linux and Windows platforms are achieved through the deployment of monitoring and switchover solutions for SAP Application Server (AS) and both JAVA and ABAP Web Application Server (WAS) environments.

Please join Steel Eye EVP of Product Management, Bob Williamson as he explains how you can minimize your downtime using SAP High Availability with SteelEye.

Reproduced with permission from https://clusteringformeremortals.com/2010/06/30/minimize-downtime-using-high-availability-clustering-and-data-replication-for-sap/

 

Will Windows Failover Clusters Become Obsolete?

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Will Windows Failover Clusters Become Obsolete?

I was recently asked whether Windows Failover Clusters (MSCS/WSFC) will become obsolete due to 3rd party HA solutions. To me, there will always be a market for 3rd party HA solutions. But many of the enhancements delivered with Windows Server 2008 have reduced the need to explore alternate HA solutions.  I think the greater threat to MSCS/WSFC is HA solutions provided by the virtualization vendors. This includes Microsoft’s Hyper-V failover clusters (which actually uses WSFC) and VMware HA.  These solutions provided by the virtualization platform provide protection in case of host failure. Although, they currently do not have visibility into the application that is running within the VM.

The real question is what kind of failure do you want to protect against? If physical server failure is your primary concern, then in some cases where MSCS may have previously been deployed, you will see Hyper-V Clusters or VMware HA being deployed instead.  In other cases where MSCS/WSFC may have seemed like overkill or was incompatible with the OS or application, you will instead see clustered VMs being deployed because it is easy to install and it supports all applications and operating systems. The mere fact that more workloads will be running per physical server will make it imperative to have some kind of clustering solution so that the failure of a single server does not bring down your entire infrastructure. In many cases, this clustering solution will be provided by the virtualization vendor.

Hyper-V Clusters and VMware HA are easy to implement and have a broad range of support as the protected VM can be running any OS or application.  The tradeoff is that you lose the application level monitoring included with MSCS/WSFC.  There will always be a class of applications that need application awareness. So MSCS/WSFC or other HA solutions that manage application availability will always be needed to ensure that the application is available, not just the server itself. With that being said, MSCS/WSFC will not become obsolete. Instead, you will see it deployed alongside other cluster solutions provided by the hypervisor vendors.

Read more about Windows Failover Clusters

Reproduced with permission from https://clusteringformeremortals.com/2010/03/01/will-windows-failover-clusters-mscswsfc-become-obsolete/

Remove The Weakest Link, Ensure High Availability Cluster Configuration

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Build A High Availability Cluster Configuration

When we build a High Availability Cluster Configuration, your application availability is only as good as its weakest link. What this means is that if you bought great servers with redundant everything (CPU, fans, power, RAID, RAM, etc) and a super deluxe SAN with multi-path connectivity. Coupled with multiple SAN switches and clustered your application with your favorite clustering software. You probably have a very reliable application – right? Well, not necessarily. Are the servers plugged into the same UPS? Are they on the same network switch? Are they cooled by the same AC unit? Are they in the same building? Is your SAN truly reliable? Any one of these issues among others is a single point of failure in a High Availability Cluster Configuration.

Seek And Remove The Weakest Link in Cluster Configuration

Of course, you have to know when “good enough” is “good enough”. Your budget and your SLAs will help decide what exactly is good enough. However, one area where I am concerned that people may be skimping is in the area of storage. With the advent of cheap or free iSCSI target software solutions, I am seeing some people recommend that you just throw some iSCSI target software on a spare server and voilà – instant shared storage.

Mind you I’m not talking about OEM iSCSI solutions that have built in failover technology and/or other availability features; or even storage virtualization solutions such as FalconStor. I’m talking about the guy who has a server running Windows Server 2008 that he has loaded up with storage and wants to turn it into an iSCSI target. This is great in a lab. But if you are serious about HA, you should think again. Even Microsoft only provides their iSCSI target software to qualified OEM builders experienced in delivering enterprise class storage arrays.

What You Are Actually Getting?

First of all, this is Windows. Not some hardened OS built to only serve storage. It will require maintenance, security updates, hardware fixes, etc. It basically has the same reliability as the application server you are trying to protect. Does it make sense to cluster your application servers. Yet use the same class of server and OS to host your storage? You basically have moved your single point of failure away from your application server and moved it to your storage server. It’s not a smart move as far as I am concerned.

Some of the Enterprise Class iSCSI target software includes synchronous and/or asynchronous replication software and snapshot capabilities. This functionality certainly helps in terms of your recovery point objective (RPO). Although it won’t help your recovery time objective (RTO) unless the failover is automatic and seamless to your clustering software. Let’s say the primary iSCSI storage array fails in the middle of the night. Who is going to be there to activate the replicated copy? You may be down for quite some time before you even realize there is a problem. Again, this may be “good enough”; you just need to be aware of what you are signing up for. Is that the High Availability Cluster Configuration you’re seeking?

SIOS DataKeeper

One thing you can do to improve the reliability of your iSCSI target server is to use a replication product such as SteelEye DataKeeper Cluster Edition to eliminate the single point of failure. Let me illustrate.

Typical Shared Storage Configuration
Figure 1 – Typical Shared Storage Configuration. In the event that the iSCSI target becomes unavailable, all the nodes go offline.

If we take the same configuration shown above and add a hot standby iSCSI target using SteelEye DataKeeper Cluster Edition to do replication AND automatic failover, you have just given you iSCSI target solution a whole new level of availability. That solution would look very much like this.

DataKeeper Cluster Edition - High Availability Cluster Configuration
Figure 2 – In this scenario, DataKeeper Cluster Edition is replicating the iSCSI attached volume on the active node to the iSCSI attached volume on the passive node, which is connected to an entirely different iSCSI target server.

The key difference in the solution which utilizes SteelEye DataKeeper Cluster Edition vs. replication solutions provide by some iSCSI target vendors is in the integration with WSFC. The question to ask of your iSCSI solution vendor is this…

What happens if I pull the power cord on the active iSCSI target server?

If the recovery process is a manual procedure, it is not a true HA solution. But what if it is automatic and completely integrated with WSFC? Then you have a much higher level of availability and have eliminated the iSCSI array as a single point of failure.

Chat with us to also achieve High Availability Cluster Configuration

Reproduced with permission from Clusteringformortals.