SIOS SANless clusters High-availability Machine Learning monitoring
Here is a great video from a friend of mine and former MVP Cluster Lead, Symon Perriman. It looks like he is enjoying his new job as Microsoft product evangelist.
http://technet.microsoft.com/en-us/edge/Hh133452
Reproduced with permission from https://clusteringformeremortals.com/2011/05/11/failover-clustering-hyper-v-multi-site-disaster-recovery/
Microsoft recently released a patch that allows you to specify whether or not a cluster node can vote in in a majority quorum model. This is particularly useful in a multisite cluster configuration that consists of an even number of nodes.
http://support.microsoft.com/kb/2494036
Consider the following…
I have a two node cluster in a local site high availability and I wish to extend it to a 3rdlocation and add a single node for disaster recovery. Sound like a great plan as a multisite cluster is just about the most robust DR plan you can implement. However, you will not be able to take advantage of one of the best features of a multisite cluster – automatic recovery in the event of a site loss. If you were to lose your primary site the DR site only contains one cluster node (see Figure 1). This is just one vote out of three in the cluster so a majority cannot be obtained and Node3 will not come online automatically. The only way to make Node3 come online is to force the quorum online, which kind of defeats the purpose of multisite cluster by requiring human intervention for a failover to happen.
The only “safe” way to have automatic failover in a multisite cluster is to have an equal number of nodes in each site and to have a file share witness in a 3rd location with connectivity back to both the primary site and the DR site. This concept is a little difficult to grasp at first, so let me attempt to explain through illustrations.
As you can see, figure 4 represents the only reasonable configuration which supports automatic failover. However, this assumes that there are an equal number of nodes in each location. If you are stuck with the original 3-node configuration you are stuck as adding a file share witness does not help as you can never achieve a majority in the alternate site…until today! Microsoft release a patch that basically allows you to specify whether or not a node gets to vote or not. So what this means is you can build a 3-node cluster as illustrated in Figure 1, yet take advantage a file share witness in a 3rd location as illustrated in Figure 4. By simply telling one of the nodes in the Primary Site to note vote in the cluster you will allow the Alternate Site to form a majority with the file share witness and come online. Assuming connectivity to your 3rd location and Alternate Site is relatively reliable there really is no downside to the configuration shown in Figure 5.
While this is a great solution, you still need that 3rd location for the file share witness. If you don’t have that 3rd location you will just have to settle for a manual switchover and keep the file share witness in the primary site if you have an even number of nodes.
The PreventQuorum switch is also included as part of this hotfix which will also be of interest to people deploying multisite clusters. Well explore that option in a future article.
Get the hot fix here…
A hotfix is available to let you configure a cluster node that does not have quorum votes in Windows Server 2008 and in Windows Server 2008 R2
http://support.microsoft.com/kb/2494036
Reproduced with permission from https://clusteringformeremortals.com/2011/04/29/microsoft-multisite-cluster18-users-rejoice-it-is-now-possible-to-have-automatic-failover-in-a-3-node-cluster19/
Now that Starwind has stopped offering a free, limited version of their iSCSI target software you might be looking for an alternative for your labs. If you need something for use in the cluster, check out Microsoft which has recently made their iSCSI target software available as part of the Windows Storage Server 2008 R2 download on Tech-Net and MSDN. It is not for use in production and has some of its own licensing restrictions, but it works fine and it is free for Tech-Net and MSDN subscribers.
I recorded some really quick and dirty videos that aim to show you how to configure the iSCSI target and iSCSI initiator software in under 7 minutes. At the end, you will have a shared disk array ready to start your shared storage cluster. Hopefully when I get some more time I’ll actually write these steps out, but in a pinch this will give you the general idea of what needs to be done. There are plenty of other features, but for a lab environment this will do the trick.
http://screencast.com/t/2qUUDvZo6Zka – configuring the iSCSI target software and iSCSI initiator on the client
http://screencast.com/t/7m9ElSIdAbP – configuring the iSCSI initiator….continued
Reproduced with permission from https://clusteringformeremortals.com/2011/03/24/configuring-the-microsoft-iscsi-target-software-for-use-in-a-cluster/
There are some reports on the newsgroups of storage validation failures after upgrading 3+ node clusters to Windows Server 2008 R2 SP1. It seems Microsoft is aware of the issue and they are investigating. I have been following this thread to keep up to date on the issue
You might want to wait for some sort of resolution before you apply SP1 to your clusters.
Reproduced with permission from https://clusteringformeremortals.com/2011/03/31/you-might-want-to-hold-off-on-the-sp1-upgrade-for-your-cluster/
Every article I read about virtualization and disaster recovery says VMware has a more robust DR solution than Microsoft. Well, I’d like to challenge that assumption. From the view where I sit, this is actually one of the areas where Microsoft has a major competitive advantage at the moment. Here is how I see it.
This is an optional additional add on that rides on the back of Array based replication solutions. The recovery point objective is good due to the array based replication. The RTO is measured in hours, not minutes. Add in the fact that moving back to the primary data center is a very manual procedure. It basically requires that you re-create your jobs in the opposite direction. The complete end to end recovery operation of failover and failback could take the better part of a day or longer.
Virtual machine HA clustering is included with the free version of Hyper-V Server 2008 R2, as well as with Windows Server 2008 Enterprise and Datacenter editions. In order to do multi-site clusters, it requires array based replication or host based replication solutions that integrate with Windows Server Failover Clustering. With a multi-site cluster, failover is measured in minutes (just about the time it takes to start a VM) and can be used with array based replication solutions such as EMC SRDF CE or HP MSA CLX or the much less expensive host based replication solutions such as SteelEye DataKeeper Cluster Edition.
Not only is failover quick with Hyper-V multi-site clusters, measured in just a few minutes. Failback is also quick and seamless as well. Add in support for Live Migrations or Quick Migration across Data Centers. I think this is one area that Microsoft actually has a much more robust solution than VMware Vsphere Disaster Recovery Options. Maybe it does not included automated DR tests, but when you consider you can failover and failback all in under 10 minutes, maybe an actual DR test performed monthly would give you a much better indication of what to expect in an actual disaster?
If you want a Hyper-V solution more like SRM, then there is an option there as well. It is called Citrix Essential for Hyper-V. But much like SRM, it is an optional add-on feature. It really doesn’t even match the RPO and RTO features that you can achieve with basic multi-site clusters for Hyper-V.
What do you think? Am I wrong or is there something I just don’t get? From my view, Hyper-V is heads and shoulders above Vsphere Disaster Recovery Options.
Reproduced with permission by https://clusteringformeremortals.com/2010/03/10/are-vmware%E2%80%99s-vsphere-disaster-recovery-options-really-better-than-microsoft%E2%80%99s-options-for-hyper-v/