The two most commonly used high availability (HA) clustering configurations are active-active and active-passive. What's the difference between the two? Here's what you need to know about active-active vs active-passive cluster nodes.
Active-Active High Availability Cluster
An active-active cluster is typically made up of at least two nodes, both actively running the same kind of service simultaneously. The main purpose of an active-active cluster is to achieve load balancing. Load balancing distributes workloads across all nodes in order to prevent any single node from getting overloaded. Because there are more nodes available to serve, there will also be a marked improvement in throughput and response times.
The set up below, which consists of a load balancer and two HTTP servers (ex. two nodes), is an example of this type of HA cluster configuration. Instead of connecting directly to an HTTP server, web clients go through the load balancer, which in turn connects each client to any of the HTTP servers behind it.
Assigning clients to the nodes in the cluster isn't an arbitrary process. Rather, it's based on which load balancing algorithm is set on the load balancer. So for example, in a "Round Robin" algorithm, the first client to connect is sent to the first server, the second client goes to the second server, the third client goes back to the first server, the fourth client back to the second server, and so on. We'll elaborate more on these algorithms in a future post.
In order for the disaster recovery cluster to operate seamlessly, we recommend that the two nodes be configured for redundancy. In other words, their individual configurations/settings must be virtually identical.
If you're interested, the tutorial How to Setup High Availability File Transfer Servers explains how to achieve redundancy between two MFT servers.
Another thing to bear in mind is that a cluster like this works best when the nodes store files in a shared storage like a NAS. Read Setting Up a NAS Shared Storage for Your File Transfer Servers for more information.
Active-Passive High Availability Cluster
Like the active-active cluster configuration, an active-passive cluster also consists of at least two nodes. However, as the name "active-passive" implies, not all nodes are going to be active. In the case of two nodes, for example, if the first node is already active, the second node must be passive or on standby.
The passive (failover) server serves as a backup that's ready to take over as soon as the active (primary) server gets disconnected or is unable to serve, an active-passive failover for when a node fails.
When clients connect to a two-node cluster in active-passive configuration, they only connect to one server. In other words, all clients will connect to the same server. Like in the active-active configuration, it's important that the two servers have exactly the same settings (ex. redundant).
If changes are made on the settings of the primary server, those changes must be cascaded to the failover server. So when the failover does take over, the clients won't be able to tell the difference.
JSCAPE has two products that enable you to set up either an active-active or active-passive (or even a combination of both) failover configuration. The first product is JSCAPE MFT Server, a managed file transfer server that supports several file transfer protocols, including FTP, FTPS, SFTP, HTTP, HTTPS, WebDAV, OFTP, AS2, AFTP, and others. Also, it's platform-agnostic and can be installed on Microsoft Windows, Linux, Mac OS X and Solaris.
The second product is JSCAPE MFT Gateway, a server application that functions both as a reverse proxy and a load balancer. It can provide the load balancing function in an active-active configuration. MFT Gateway supports multiple load balancing algorithms, including Round Robin, Weighted Round Robin, Random, Least Connections, and Weighted Least Connections.
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Would you like to try this yourself? JSCAPE MFT Server is platform-agnostic and can be installed on Microsoft Windows, Linux, Mac OS X and Solaris, and can handle any file transfer protocol as well as multiple protocols from a single server. Additionally, JSCAPE enables you to handle any file type, including batch files and XML. Download your free 7-day trial of JSCAPE MFT Server now.
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