VIP mode
In high availability (HA) systems, a Virtual IP (VIP) is an abstract IP. It can move between nodes/servers to keep services reachable.
When you design a VIP-based HA setup, you typically choose one mode: Active/Active or Active/Passive.
Choosing the right mode affects architecture, performance, and cost.
1. Active/Active Mode
Definition
In Active/Active, all nodes are active at the same time. They all receive and process traffic. Nodes coordinate to keep data consistent and performance stable.
Key characteristics
Load distribution: A load balancer spreads traffic across nodes.
Higher throughput and easier scale-out: Add nodes with minimal disruption.
High availability: If one node fails, others keep serving traffic.
More complexity: Requires solid data sync and load-balancing design.
Real-world examples
Web server clusters: Run multiple web nodes behind NGINX or AWS ELB.
Distributed databases: Systems like Cassandra or CockroachDB.
CDNs: Cloudflare or Akamai run many edge nodes in parallel.
2. Active/Passive Mode
Definition
In Active/Passive, only one node is Active at any time. The other node is Passive and stays on standby.
If the active node fails, the VIP moves to the passive node. Service resumes after a short failover window.
Key characteristics
Simpler operations: One active node is easier to observe and debug.
Safe redundancy: The standby node is ready to take over.
Lower cost: One node serves traffic, one waits.
Brief downtime on failover: Seconds to minutes, depending on setup.
Real-world examples
Database failover: SQL Server clusters, or MySQL primary/replica.
HA firewalls: One active firewall, one standby firewall.
Internal enterprise apps: ERP/CRM/accounting systems with steady traffic.
3. Overall comparison
Criteria
Active/Active
Active/Passive
Performance
High, traffic shared across nodes
Lower, only one node handles traffic
Availability
Minimal interruption (near-zero downtime)
Brief interruption during failover
Cost
Higher (multiple active nodes)
Lower (one active, one standby)
Complexity
Higher (sync, load balancing)
Lower (mainly failover configuration)
Best fit
Large web systems, distributed platforms
Internal apps, cost-sensitive systems
4. Recommended model
Active/Active fits mission-critical systems and high traffic workloads. It also fits multi-zone or multi-region designs.
Active/Passive fits internal apps and cost-focused setups. It also fits workloads that can tolerate brief failover.
No downtime tolerated
Active/Active
High throughput required
Active/Active
Small system, cost first
Active/Passive
Can tolerate brief downtime
Active/Passive
Last updated