Amazon EC2 offers several purchasing options to help optimize costs based on your workload requirements. Understanding these options is crucial for the AWS Certified SysOps Administrator exam.
**On-Demand Instances** provide the most flexibility, allowing you to pay for compute capacity by the hou…Amazon EC2 offers several purchasing options to help optimize costs based on your workload requirements. Understanding these options is crucial for the AWS Certified SysOps Administrator exam.
**On-Demand Instances** provide the most flexibility, allowing you to pay for compute capacity by the hour or second with no long-term commitments. These are ideal for unpredictable workloads, testing, and development environments.
**Reserved Instances (RIs)** offer significant discounts (up to 72%) compared to On-Demand pricing in exchange for a 1 or 3-year commitment. You can choose between Standard RIs (highest discount, less flexibility) and Convertible RIs (lower discount, ability to change instance attributes). Payment options include All Upfront, Partial Upfront, and No Upfront.
**Savings Plans** provide flexible pricing similar to Reserved Instances but apply across instance families, regions, and compute services. Compute Savings Plans offer the most flexibility, while EC2 Instance Savings Plans provide deeper discounts for specific instance families.
**Spot Instances** allow you to bid on unused EC2 capacity at discounts up to 90% off On-Demand prices. However, AWS can reclaim these instances with a 2-minute notification when capacity is needed. Spot Instances are perfect for fault-tolerant, flexible applications like batch processing and big data analytics.
**Dedicated Hosts** provide physical servers dedicated to your use, helping meet compliance requirements and allowing you to use existing server-bound software licenses. **Dedicated Instances** run on hardware dedicated to a single customer but dont provide visibility into the underlying host.
**Capacity Reservations** ensure you have EC2 capacity available when needed in a specific Availability Zone, useful for disaster recovery or regulatory requirements.
For the SysOps exam, understand how to combine these options strategically—using Reserved Instances for baseline capacity, On-Demand for variable workloads, and Spot Instances for cost optimization on interruptible tasks.
EC2 Instance Purchasing Options
Why It Is Important
Understanding EC2 instance purchasing options is crucial for the AWS SysOps Administrator Associate exam because it directly impacts cost optimization, which is a major responsibility of system administrators. Choosing the right purchasing option can reduce AWS costs by up to 72% compared to On-Demand pricing. The exam frequently tests your ability to recommend the most cost-effective solution for different workload scenarios.
What Are EC2 Instance Purchasing Options?
AWS offers several ways to pay for EC2 instances, each designed for different use cases:
1. On-Demand Instances Pay by the hour or second with no long-term commitments. Best for unpredictable workloads, testing, and development environments.
2. Reserved Instances (RIs) Commit to a 1 or 3-year term for significant discounts (up to 72%). Available in three payment options: All Upfront, Partial Upfront, and No Upfront. Can be Standard RIs (higher discount, less flexibility) or Convertible RIs (lower discount, can change instance family).
3. Savings Plans Flexible pricing model offering savings up to 72%. Commit to a consistent amount of usage (measured in $/hour) for 1 or 3 years. Includes Compute Savings Plans and EC2 Instance Savings Plans.
4. Spot Instances Purchase unused EC2 capacity at up to 90% discount. Instances can be interrupted with a 2-minute warning. Best for fault-tolerant, flexible, and stateless workloads.
5. Dedicated Hosts Physical servers fully dedicated to your use. Required for server-bound software licenses. Most expensive option.
6. Dedicated Instances Instances running on hardware dedicated to a single customer. Less control than Dedicated Hosts but still provides hardware isolation.
7. Capacity Reservations Reserve capacity in a specific Availability Zone. Ensures you have capacity when needed. Can be combined with Savings Plans for cost benefits.
How It Works
When launching EC2 instances, you select a purchasing option based on your workload requirements:
- Stable, predictable workloads: Use Reserved Instances or Savings Plans for maximum cost savings - Variable workloads: Use On-Demand for the baseline and Spot for additional capacity - Batch processing or big data: Use Spot Instances since these workloads can handle interruptions - Compliance requirements: Use Dedicated Hosts or Dedicated Instances when hardware isolation is mandated
Reserved Instances can be scoped to a Region (more flexibility) or Availability Zone (capacity reservation included). Standard RIs can be sold in the Reserved Instance Marketplace if no longer needed.
Exam Tips: Answering Questions on EC2 Instance Purchasing Options
Key Scenarios to Recognize:
1. When you see cost optimization with steady-state workloads, think Reserved Instances or Savings Plans
2. When you see fault-tolerant, flexible, or stateless applications, think Spot Instances
3. When you see licensing requirements or bring your own license (BYOL), think Dedicated Hosts
4. When you see compliance or regulatory requirements for hardware isolation, think Dedicated Hosts or Dedicated Instances
5. When you see short-term, unpredictable, or testing workloads, think On-Demand
6. When you see guaranteed capacity in a specific AZ, think Capacity Reservations
Important Details to Remember:
- Spot Instances provide the highest discount (up to 90%) - Reserved Instances with All Upfront payment provide the highest RI discount - Convertible RIs allow you to change instance families but offer lower discounts than Standard RIs - Savings Plans provide more flexibility than Reserved Instances - Dedicated Hosts give visibility into sockets and physical cores (important for licensing) - Spot Fleet can automatically request a mix of Spot and On-Demand instances
Common Exam Traps:
- Do not recommend Spot Instances for databases or stateful applications - Do not confuse Dedicated Hosts with Dedicated Instances; Hosts provide more control - Remember that Regional Reserved Instances provide flexibility across AZs but do not include capacity reservation