Multi-AZ deployment for high availability in AWS - Step-by-Step Execution

Process Flow - Multi-AZ deployment for high availability

Start Deployment

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Select Primary AZ

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Deploy Primary Instance

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Select Secondary AZ

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Deploy Secondary Instance

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Configure Sync & Failover

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Monitor Health

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If Primary Fails?

Yes→Failover to Secondary

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Continue Serving

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Deployment Complete

This flow shows deploying resources in two separate availability zones to ensure service stays up if one zone fails.

Execution Sample

AWS

Create EC2 in AZ1
Create EC2 in AZ2
Configure Load Balancer
Set Health Checks
Enable Auto Failover

This sequence deploys two instances in different zones, sets up a load balancer, and configures failover for high availability.

Process Table

Step	Action	Resource State	Result
1	Select Primary AZ	Primary AZ set to us-east-1a	Primary AZ chosen
2	Deploy Primary Instance	EC2 instance running in us-east-1a	Primary instance active
3	Select Secondary AZ	Secondary AZ set to us-east-1b	Secondary AZ chosen
4	Deploy Secondary Instance	EC2 instance running in us-east-1b	Secondary instance active
5	Configure Load Balancer	Load Balancer routing to both instances	Traffic balanced
6	Set Health Checks	Health checks monitoring both instances	Monitoring active
7	Enable Auto Failover	Failover configured to secondary instance	Failover ready
8	Primary Instance Fails	Primary instance down	Failover triggers to secondary
9	Secondary Instance Serves Traffic	Secondary instance active	Service continues without downtime
10	Primary Instance Recovers	Primary instance back online	Failback possible
11	Deployment Complete	Both instances running, failover active	High availability ensured

💡 Deployment completes with both instances active and failover configured for high availability.

Status Tracker

Variable	Start	After Step 2	After Step 4	After Step 7	After Step 9	Final
Primary AZ	unset	us-east-1a	us-east-1a	us-east-1a	us-east-1a	us-east-1a
Secondary AZ	unset	unset	us-east-1b	us-east-1b	us-east-1b	us-east-1b
Primary Instance	not running	running	running	running	down	running
Secondary Instance	not running	not running	running	running	running	running
Load Balancer	not configured	not configured	not configured	configured	configured	configured
Failover Status	disabled	disabled	disabled	enabled	enabled	enabled

Key Moments - 3 Insights

Why do we deploy instances in different AZs instead of the same AZ?

Deploying in different AZs protects against zone failure. Execution table rows 2 and 4 show instances in separate AZs, ensuring if one AZ fails (row 8), the other can serve traffic (row 9).

What triggers the failover to the secondary instance?

Failover triggers when health checks detect the primary instance is down (row 8). This causes traffic to switch to the secondary instance (row 9), maintaining availability.

Can the system switch back to the primary instance after it recovers?

Yes, after the primary instance recovers (row 10), failback can occur to restore the primary as active, as shown in the deployment completion (row 11).

Visual Quiz - 3 Questions

Look at the execution table, at which step is the secondary instance deployed?

A Step 4

B Step 2

C Step 6

D Step 8

💡 Hint

Check the 'Action' column for 'Deploy Secondary Instance' in the execution table.

According to the variable tracker, what is the state of the primary instance after step 9?

A Running

B Down

C Not Running

D Starting

💡 Hint

Look at the 'Primary Instance' row under 'After Step 9' in the variable tracker.

If failover was not enabled at step 7, what would happen at step 8 when the primary instance fails?

A Primary instance would auto-recover immediately

B Traffic would continue to secondary instance

C Service would experience downtime

D Load balancer would shut down

💡 Hint

Refer to the 'Failover Status' variable in the tracker and the failover action in the execution table.

Concept Snapshot

Multi-AZ deployment means placing resources in two separate availability zones.
This protects your service if one zone fails.
Deploy primary and secondary instances in different AZs.
Use a load balancer to route traffic.
Set health checks and enable automatic failover.
This setup keeps your service running without downtime.

Full Transcript

Multi-AZ deployment for high availability involves deploying resources in two different availability zones to protect against zone failure. First, you select a primary AZ and deploy an instance there. Then, you select a secondary AZ and deploy a second instance. A load balancer is configured to route traffic to both instances, and health checks monitor their status. Failover is enabled so that if the primary instance fails, traffic automatically switches to the secondary instance, ensuring continuous service. When the primary recovers, failback can restore it as the active instance. This approach ensures your service remains available even if one AZ goes down.