Load balancing Swiftstack

How to load balance SwiftStack

SwiftStack Storage architecture supports High Availability (HA) clustering by putting a load balancer in front of it.

Load balancers monitor and perform health checks on a node to ensure traffic is routed correctly to healthy nodes. Without the use of a load balancer, an offline or failed node would still receive traffic, causing failures.

For load balancing Swiftstack Storage we recommend Layer 4 Direct Routing (DR) mode, sometimes referred to as Direct Server Return (DSR). However, Layer 4 NAT, Layer 4 SNAT and Layer 7 SNAT can also be used. The best method for your deployment depends on a variety of factors. Layer 4 DR mode is fastest, but requires the ARP problem to be solved, and the application running on the real servers to respond both to its own IP address and the VIP. Layer 4 NAT mode requires the default gateway on the real servers to be the load balancer. Layer 4 SNAT mode doesn’t require real server changes, but unlike the other Layer 4 methods, is non-transparent. Layer 7 SNAT mode is also non-transparent and requires no real server changes – but it doesn’t offer the raw throughput of Layer 4 methods.

Example Layer 4 DR configuration

With Layer 4 Direct Routing, a node does not rely on sending its reply traffic via the load balancer. Instead, the back-end nodes have the VIP or load balancer address attached to their local interface, and so can send a TCP reply directly back to the client with the source address the client is expecting.