VMware High Availability vs. Fault Tolerance
Introduction
VMware HA and FT are indispensable tools for ensuring uninterrupted operations and maintaining business continuity. VMware HA offers rapid recovery in case of host failures, while VMware FT takes it a step further by providing true fault tolerance with zero downtime. By leveraging these virtualization technologies, organizations can minimize the impact of unexpected disruptions and deliver a seamless experience to their customers, ultimately bolstering their competitive edge in the market.
VMware HA (High Availability)
VMware HA is suitable for workloads where short periods of downtime are acceptable and can be tolerated. It's a cost-effective solution that provides rapid recovery for VMs in the event of host hardware or software failures. It's like having a safety net for your VMs, ensuring that they remain available even when the underlying infrastructure encounters issues.
How VMware HA works
Monitoring: VMware HA continuously monitors the health of ESXi hosts within a cluster. If it detects any abnormalities or failures, such as a host going offline, it triggers a response.
Response: When an issue is detected, HA will attempt to restart the VMs affected on healthy hosts within the same cluster. This process is automated and happens within minutes, minimizing downtime.
Admission Control: HA also employs an Admission Control mechanism to prevent resource overcommitment. This ensures that there are enough resources available to accommodate the VMs in the event of a failure.
Network Isolation: HA can also detect network isolation scenarios, where a host loses connectivity with the rest of the cluster. In such cases, it takes actions to prevent split-brain situations and maintain VM availability.
VMware FT (Fault Tolerance)
VMware FT is designed for applications that demand continuous, uninterrupted operations. While HA helps recover from failures, VMware Fault Tolerance (FT) takes availability to the next level by eliminating downtime altogether. FT ensures continuous operation of VMs without any interruption, even in the face of host failures.
How VMware FT works
Real-Time Replication: FT creates an identical copy of a VM, known as a "shadow VM," on a secondary host. This shadow VM replicates all the instructions and data from the primary VM in real-time.
Synchronized Execution: Both the primary VM and the shadow VM run in lockstep, executing the exact same instructions simultaneously. This ensures that if the primary VM encounters a failure, the shadow VM seamlessly takes over without any data loss or downtime.
Zero RPO and RTO: FT guarantees a zero Recovery Point Objective (RPO) and a near-zero Recovery Time Objective (RTO), making it ideal for mission-critical applications that demand continuous availability.