# Multi-Region Deployment Strategy

## Overview

This deployment uses **multi-region architecture** with **different VM families per region** to maximize utilization of available quotas without requiring quota increases.

## Subscription Information

- **Subscription ID**: `6d3c4263-bba9-497c-8843-eae6c4e87192`
- **Regions**: West Europe, North Europe, France Central
- **Strategy**: Distribute workload across regions using different VM families

## Available Quotas by Region

### West Europe (Primary)

| VM Family | Available | Used | Total |
|-----------|-----------|------|-------|
| Standard DSv3 Family | 4 | 6 | 10 |
| Standard D Family | 10 | 0 | 10 |
| Standard Dv2 Family | 10 | 0 | 10 |
| Standard Dv2 Promo Family | 10 | 0 | 10 |
| Standard Dsv6 Family | 10 | 0 | 10 |
| Standard Av2 Family | 10 | 0 | 10 |

**Total Available**: ~54 vCPUs across different families

### Deployment Plan: West Europe

| Node Pool | VM Size | Family | Nodes | vCPUs | Quota Used |
|-----------|---------|--------|-------|-------|------------|
| System | Standard_D2s_v3 | DSv3 | 2 | 4 | DSv3: 4/10 |
| Validators | Standard_D4_v2 | Dv2 | 2 | 8 | Dv2: 8/10 |
| Sentries | Standard_D4s_v6 | Dsv6 | 2 | 8 | Dsv6: 8/10 |
| RPC | Standard_D8_v2 | Dv2 | 1 | 8 | Dv2: 8/10 |
| **Total** | | | **7** | **28** | **Within limits** |

### North Europe (Secondary)

| Node Pool | VM Size | Family | Nodes | vCPUs |
|-----------|---------|--------|-------|-------|
| System | Standard_D2s_v3 | DSv3 | 1 | 2 |
| Validators | Standard_D4_v2 | Dv2 | 1 | 4 |
| Sentries | Standard_D4s_v6 | Dsv6 | 1 | 4 |
| RPC | Standard_D8_v2 | Dv2 | 1 | 8 |
| **Total** | | | **4** | **18** |

### France Central (Tertiary)

| Node Pool | VM Size | Family | Nodes | vCPUs |
|-----------|---------|--------|-------|-------|
| System | Standard_D2s_v3 | DSv3 | 1 | 2 |
| Validators | Standard_D4_v2 | Dv2 | 1 | 4 |
| Sentries | Standard_D4s_v6 | Dsv6 | 1 | 4 |
| RPC | Standard_D8_v2 | Dv2 | 1 | 8 |
| **Total** | | | **4** | **18** |

## Total Multi-Region Deployment

| Region | Nodes | vCPUs |
|--------|-------|-------|
| West Europe | 7 | 28 |
| North Europe | 4 | 18 |
| France Central | 4 | 18 |
| **Total** | **15** | **64** |

## VM Family Distribution

### Why Different Families?

1. **Quota Optimization**: Each VM family has separate quotas
2. **Cost Efficiency**: Dv2 and Dsv6 families may have better pricing
3. **Availability**: Reduces dependency on single family quota
4. **Performance**: Different families for different workloads

### VM Family Specifications

| Family | Characteristics | Use Case |
|--------|----------------|----------|
| **DSv3** | Premium SSD, latest gen | System nodes (low latency) |
| **Dv2** | Standard SSD, proven | Validators, RPC (cost-effective) |
| **Dsv6** | Premium SSD, latest gen | Sentries (high performance) |

## Deployment Steps

### 1. Enable Multi-Region Deployment

```bash
cd terraform
cp terraform.tfvars.multi-region terraform.tfvars
```

### 2. Review Configuration

Edit `terraform/multi-region.tf` to adjust:
- Node counts per region
- VM families per region
- Regions to deploy

### 3. Initialize Terraform

```bash
terraform init
```

### 4. Plan Deployment

```bash
terraform plan -out=tfplan
```

### 5. Apply Deployment

```bash
terraform apply tfplan
```

## Benefits of Multi-Region Deployment

1. **High Availability**: Geographic redundancy
2. **Quota Utilization**: Uses available quotas across regions
3. **Performance**: Lower latency for regional users
4. **Disaster Recovery**: Automatic failover capability
5. **Compliance**: Data residency options

## Network Architecture

### Cross-Region Connectivity

- **VNet Peering**: Connect VNets across regions
- **Private Endpoints**: Secure cross-region communication
- **Application Gateway**: Global load balancing
- **DNS**: Multi-region DNS resolution

### Traffic Distribution

- **Primary**: West Europe (28 vCPUs, 7 nodes)
- **Secondary**: North Europe (18 vCPUs, 4 nodes)
- **Tertiary**: France Central (18 vCPUs, 4 nodes)

## Cost Optimization

### Estimated Monthly Costs (Approximate)

| Region | Resource | Cost/Month |
|--------|----------|------------|
| West Europe | 7 nodes (mixed families) | ~$500-700 |
| North Europe | 4 nodes (mixed families) | ~$300-400 |
| France Central | 4 nodes (mixed families) | ~$300-400 |
| **Total** | **15 nodes** | **~$1,100-1,500** |

*Note: Costs vary based on VM sizes, usage, and Azure pricing*

## Monitoring

### Multi-Region Monitoring

- **Azure Monitor**: Cross-region metrics
- **Log Analytics**: Centralized logging
- **Application Insights**: End-to-end tracing
- **Grafana**: Multi-region dashboards

## Disaster Recovery

### Failover Strategy

1. **Automatic**: Kubernetes cluster autoscaling
2. **Manual**: Traffic routing via Application Gateway
3. **DNS**: Failover via Cloudflare DNS

## Next Steps

1. ✅ Review quota availability in all regions
2. ✅ Configure multi-region Terraform
3. ⏳ Deploy primary region (West Europe)
4. ⏳ Deploy secondary regions (North Europe, France Central)
5. ⏳ Configure cross-region networking
6. ⏳ Set up global load balancing
7. ⏳ Configure monitoring and alerting

## Troubleshooting

### Quota Issues

If a region runs out of quota:
1. Check alternative VM families
2. Reduce node counts in that region
3. Add additional regions
4. Request quota increase for specific family

### Network Issues

If cross-region connectivity fails:
1. Verify VNet peering
2. Check NSG rules
3. Validate private endpoints
4. Review Application Gateway configuration