Not every organisation looses millions of dollar per second but some does. An organisation may not loose millions of dollar per second but consider customer service and reputation are number one priority. These type of business wants their workflow to be seamless and downtime free. This article is for them who consider business continuity equals money well spent. Here is how it is done:
Multi-Site Failover Cluster
Microsoft Multi-Site Failover Cluster is a group of Clustered Nodes distribution through multiple sites in a region or separate region connected with low latency network and storage. As per the diagram illustrated below, Data Center A Cluster Nodes are connected to a local SAN Storage, while replicated to a SAN Storage on the Data Center B. Replication is taken care by a identical software defined storage on each site. Software defined storage will replicate volumes or Logical Unit Number (LUN) from primary site in this example Data Center A to Disaster Recovery Site B. Microsoft Failover cluster is configured with pass-through storage i.e. volumes and these volumes are replication to DR site. In the Primary and DR sites, physical network is configured using Cisco Nexus 7000. Data network and virtual machine network are logically segregated in Microsoft System Center VMM and physical switch using virtual local area network or VLAN. A separate Storage Area Network (SAN) is created in each site with low latency storage. Volumes of pass-through storage are replicated to DR site using identical size of volumes.
Figure: Highly Available Multi-site Cluster
Figure: Software Defined Storage in Each Site
Design Components of Storage:
- SAN to SAN replication must be configured correctly
- Initial must be complete before Failover Cluster is configured
- MPIO software must be installed on the cluster Nodes (N1, N2…N6)
- Physical and logical multipathing must be configured
- If Storage is presented directly to virtual machines or cluster nodes then NPIV must configured on the Fabric Zones.
- All Storage and Fabric Firmware must up to date with manufacturer latest software
- An identical software defined storage must be used on the both sites
- If a third party software is used to replicate storage between sites then storage vendor must be consulted before the replication.
Design Components of Network:
- Isolate management, virtual and data network using VLAN
- Use a reliable IPVPN or Fibre optic provider for the replication over the network
- Eliminate all single point of failure from all network components
- Consider stretched VLAN for multiple sites
Design failover Cluster Quorum
- Use Node & File Share Witness (FSW) Quorum for even number of Cluster Nodes
- Connect File Share Witness on to the third Site
- Do not host File Share Witness on a virtual machine on same site
- Alternatively use Dynamic Quorum
Design of Compute
- Use reputed vendor to supply compute hardware compatible with Microsoft Hyper-v
- Make sure all latest firmware updates are applied to Hyper-v host
- Make manufacture provide you with latest HBA software to be installed on Hyper-v host
Implementing a Multi-Site Failover Cluster
Step1: Prepare Network, Storage and Compute
Step2: Configure Failover Cluster on Each Site
Step3: Replicate Volumes
Use case can be determined by current workloads and future workloads plus business continuity. Deploy Veeam One to determine current workloads on your infrastructure and propose a future workload plus business continuity. Here is a list of use cases of multi-site cluster.
Scale-Out File Server for application data- To store server application data, such as Hyper-V virtual machine files, on file shares, and obtain a similar level of reliability, availability, manageability, and high performance that you would expect from a storage area network. All file shares are simultaneously online on all nodes. File shares associated with this type of clustered file server are called scale-out file shares. This is sometimes referred to as active-active.
File Server for general use – This type of clustered file server, and therefore all the shares associated with the clustered file server, is online on one node at a time. This is sometimes referred to as active-passive or dual-active. File shares associated with this type of clustered file server are called clustered file shares.