SQL Server on AWS: RDS vs. EC2 – Which One is Better?

When deploying Microsoft SQL Server on Amazon Web Services (AWS), you have two primary options:

1️⃣ Amazon RDS for SQL Server (Managed Database Service)
2️⃣ SQL Server on Amazon EC2 (Self-Managed Virtual Machines)

Choosing between them depends on cost, control, scalability, and maintenance effort. This guide compares both options to help you decide which is best for your workload.

1. Overview: AWS RDS vs. EC2 for SQL Server

Feature

Amazon RDS for SQL Server

SQL Server on EC2

Management

Fully managed by AWS

Self-managed

Administration

No OS/SQL patching needed

Full admin control

Scalability

Vertical scaling only

Vertical + Horizontal

High Availability (HA)

Multi-AZ deployments

Custom HA (Always On AGs, Failover Clustering)

Backup & Recovery

Automated backups + PITR

Self-configured

Cost

Higher (license included)

Lower (BYOL option)

Customization

Limited (No SQL Agent jobs, limited tempdb config)

Full control

Use Case

Best for lift-and-shift with minimal management

Best for custom setups, enterprise workloads

2. Key Differences Explained

✅ Amazon RDS for SQL Server (Managed Service)

  • Pros:

    • No server maintenance (AWS handles patching, backups, failover).

    • Built-in HA with Multi-AZ deployments (automatic failover).

    • Automated backups & Point-in-Time Recovery (PITR).

    • Easier to set up (ideal for small to medium workloads).

  • Cons:

    • Limited customization (No SQL Agent, no tempdb tuning, no linked servers).

    • No Always On AGs (only Multi-AZ synchronous replication).

    • Higher cost (license included, no BYOL in Standard Edition).

Best For:

✔ Companies that want minimal database administration.
✔ Dev/Test environments where ease of use > customization.
✔ Small to medium-sized OLTP workloads.

✅ SQL Server on EC2 (Self-Managed)

  • Pros:

    • Full control (Install any SQL version, configure tempdb, use SQL Agent).

    • Custom HA/DR (Always On AGs, Log Shipping, Failover Clustering).

    • Bring Your Own License (BYOL) → Cost savings for Enterprise Edition.

    • Better for large-scale workloads (custom tuning, memory optimization).

  • Cons:

    • More maintenance (OS patching, SQL updates, backups).

    • Manual HA setup (requires configuring Always On AGs or clustering).

    • Slower deployment (must provision & configure everything).

Best For:

✔ Enterprise workloads needing high customization.
✔ Legacy apps requiring SQL Agent, linked servers, or complex configurations.
✔ Cost-sensitive setups (BYOL for Enterprise Edition).

3. Pricing Comparison

Amazon RDS for SQL Server

  • License-included pricing (more expensive, but no separate SQL license needed).

  • Example:

    • db.m5.xlarge (4 vCPU, 16GB RAM)

      • SQL Server Standard: ~$1,200/month

      • SQL Server Enterprise: ~$3,500/month

SQL Server on EC2 (BYOL - Bring Your Own License)

  • Cheaper for long-term use (if you already own SQL Server licenses).

  • Example:

    • m5.xlarge (4 vCPU, 16GB RAM)

      • EC2 Cost: ~$150/month (Linux) or ~$230/month (Windows)

      • + SQL Server License (if BYOL): One-time cost (saves long-term).

💡 Tip: Use the AWS Pricing Calculator (calculator.aws) for exact estimates.

4. Performance & Scalability

Factor

RDS for SQL Server

SQL Server on EC2

Storage Options

EBS (gp2/io1)

EBS (gp3/io2), Instance Store (NVMe)

Max Memory

Up to 3TB (RDS Optimized)

Up to 24TB (EC2 High-Memory)

Max vCPUs

96 vCPUs (RDS Optimized)

128 vCPUs (EC2)

TempDB Tuning

Limited (AWS-managed)

Fully customizable

🔹 For high-performance OLTP, EC2 with NVMe storage often outperforms RDS.
🔹 For read-heavy workloads, RDS Read Replicas can help.

5. High Availability (HA) & Disaster Recovery (DR)

RDS for SQL Server

  • Multi-AZ Deployment: Automatic failover (5-10 min downtime).

  • Read Replicas: For scaling read workloads.

SQL Server on EC2

  • Always On Availability Groups (AGs): Near-zero downtime (<30 sec failover).

  • Failover Clustering: For instance-level HA.

  • Log Shipping/Backups: Manual DR setup.

💡 For mission-critical apps, EC2 + Always On AGs is the best choice.

6. Security & Compliance

Feature

RDS for SQL Server

SQL Server on EC2

Encryption at Rest

 (AWS KMS)

(AWS KMS or TDE)

Network Isolation

(VPC, Security Groups)

(VPC, Security Groups)

Audit Logging

(AWS CloudTrail)

(SQL Server Audit + CloudWatch)

🔹 RDS is easier (AWS manages security patches).
🔹 EC2 offers more control (custom firewalls, Active Directory integration).

7. When to Choose RDS vs. EC2?

Choose Amazon RDS for SQL Server If:

✔ You want minimal administration (AWS handles backups, patching, HA).
✔ You don’t need SQL Agent, linked servers, or advanced tuning.
✔ Your workload fits Standard/Web Edition (Enterprise is expensive).

Choose SQL Server on EC2 If:

✔ You need full control (SQL Agent, tempdb tuning, custom HA).
✔ You have Enterprise Edition licenses (BYOL) → Cost savings.
✔ You run large, complex databases (OLAP, data warehouses).

8. Migration Tips

  • From On-Premises to RDS: Use AWS Database Migration Service (DMS).

  • From RDS to EC2: Take a backup → Restore on EC2.

  • For minimal downtime: Use log shipping or Always On AGs.

Final Verdict

Scenario

Best Choice

"I hate managing SQL Server!"

Amazon RDS

"I need full control & high performance"

EC2 + BYOL

"I need Enterprise features (AGs, SQL Agent)"

EC2

"I want automated backups & easy scaling"

RDS

🤔 Need Help Deciding?

Tell me your: 

🔸 SQL Server Edition (Standard/Enterprise)
🔸 Workload Type (OLTP/OLAP)
🔸 Downtime Tolerance
🔸 Budget Constraints

💡 I’ll recommend the best AWS setup for your use case! 🚀

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