Tuần 10 - Ngày 2: Reserved Instances và Savings Plans Deep Dive
Mục tiêu học tập
- So sánh RI và Savings Plans
- Hiểu Compute SP vs EC2 Instance SP
- Áp dụng strategy mix RI/SP/On-Demand
- Quản lý RI Marketplace
1. Reserved Instances (RI) Recap
Term
- 1 hoặc 3 năm commitment
- Discount lên đến 72%
Payment options
- All Upfront (AURI): most discount
- Partial Upfront (PURI): medium
- No Upfront (NURI): least discount
Offering Class
- Standard RI: locked attributes, can sell on Marketplace
- Convertible RI: exchange to other instances (cùng giá trị trở lên), cannot sell
Scope
- Regional RI (default): apply to any AZ in Region, no capacity reservation
- Zonal RI: 1 AZ, capacity reservation included
Applies to
- EC2, RDS, ElastiCache, OpenSearch, Redshift, DynamoDB
2. Savings Plans (SP) Recap
Commitment
- $/hour for 1 or 3 years
- e.g., commit $5/hour for 1 year → $$$$ savings
3 types
- Compute Savings Plans: most flexible
- EC2 Instance Savings Plans: limited to 1 family + region
- SageMaker Savings Plans: for SageMaker
Applies to
- Compute SP: EC2 (any family, region, OS, tenancy), Fargate, Lambda
- EC2 Instance SP: 1 family, 1 region, any OS/tenancy/size
- SageMaker SP: SageMaker training/inference
3. RI vs Savings Plans Comparison
| Feature | Reserved Instance | Savings Plans |
|---|---|---|
| Commitment | Specific instance attributes | $/hour spend |
| Applies to | Specific service (EC2/RDS/etc.) | Compute (EC2+Fargate+Lambda) or EC2 family |
| Flexibility | Convertible RI = some | Compute SP = highest |
| Marketplace | Standard RI can sell | Cannot sell |
| Discount | Up to 72% | Up to 72% |
| Discount priority | RI applies first | SP applies after RI |
| Use case | Specific predictable workload | Flexible compute commitment |
Discount Application Order
1. AWS-generated discounts (free tier, promotional credits)
2. Reserved Instance discounts
3. Savings Plans discounts (after RI)
4. Remaining usage at On-Demand rate
4. Detailed: Compute Savings Plans
Flexibility
- Switch EC2 family (m5 → c5 → r5)
- Switch region
- Switch OS (Linux → Windows)
- Switch tenancy
- Apply to Fargate, Lambda
Use case
- Multi-region apps
- Workload may evolve (migrate to Fargate, Lambda)
- Most cost-conscious teams
Discount
- Up to 66%
5. Detailed: EC2 Instance Savings Plans
Flexibility
- Same family (e.g., m5) + same region
- Switch size (m5.large → m5.xlarge)
- Switch OS
- Switch tenancy
Use case
- Specific EC2 family standardization
- Known region
Discount
- Up to 72% (highest within SP)
6. Combining RI + SP + On-Demand
Best practice mix
Baseline 24/7 workload → Reserved Instance 3y AURI (72% off)
Variable 80% of week → Savings Plans 1y (66% off)
Peak hourly burst → On-Demand (no commitment)
Background batch → Spot (90% off)
Example calculation
- Workload: 10 EC2 m5.large baseline + 5 peak during business hours
Strategy A: 100% On-Demand
- 15 instances × $0.10/hr × 730 hr = $1,095/month
Strategy B: Mix RI + On-Demand
- 10 RI 3y AURI: 10 × $0.04/hr × 730 = $292/month
- 5 On-Demand peak (8 hr/day, 22 days): 5 × $0.10 × 176 = $88
- TOTAL: $380/month (saving 65%)
7. RI Utilization Best Practices
Track utilization
- Cost Explorer → Reserved Instance Utilization report
- Target: 90%+
- Below 50%: waste, consider modify
Improve utilization
- Regional RI > Zonal RI (more flexible)
- Convertible RI for changing workload
- Standard RI for predictable
Sell on Marketplace (Standard RI only)
- List remaining term
- Buyers purchase shorter-term RIs
- Recover cost when no longer needed
8. Savings Plans Utilization
Track
- Cost Explorer → Savings Plans Utilization
- Target: 90%+
- Below 70%: review
Optimize
- Right-size commitment (don't over-commit)
- Use Compute SP for flexibility
- Stack multiple SPs for granularity
Cannot resell
- Avoid over-committing
9. Capacity Reservations (ODCR)
Định nghĩa
On-Demand Capacity Reservation = reserve capacity (instance available when needed) without commitment.
Đặc điểm
- No discount on price (same as On-Demand)
- Reserve capacity in specific AZ
- Cancel anytime
- Can combine với SP/RI for discount
Use case
- Critical events (Black Friday, product launch)
- DR scenario (ensure capacity for failover)
- Stable workload needing AZ-specific capacity
vs Zonal RI
- Zonal RI: capacity + discount + 1y/3y commitment
- ODCR: capacity only, no commitment, can pair với SP/RI for discount
10. RI Pricing Math Example
Scenario: 1 m5.large 24/7 for 3 years (us-east-1, Linux)
| Pricing | $/hour | 3-year total | Saving |
|---|---|---|---|
| On-Demand | $0.096 | $2,524 | 0% |
| 1-year No Upfront RI | $0.067 | $1,760 | 30% |
| 1-year All Upfront RI | $0.063 | $1,650 | 35% |
| 3-year No Upfront RI | $0.042 | $1,104 | 56% |
| 3-year All Upfront RI | $0.033 | $867 | 66% |
| Compute SP 3y AURI | $0.034 | $895 | 64% |
| EC2 SP 3y AURI | $0.030 | $789 | 69% |
Numbers approximate, verify on AWS Pricing.
11. Free Trial / Credits
Free Tier
- 12 months free (e.g., 750 EC2 t2.micro hours)
- Always-free services (Lambda 1M requests)
AWS Credits
- Promotional credits (events, contests)
- Apply to specific services or all
- Expire after period
AWS Activate (startups)
- Up to $100K credits for startup founders
12. Common Pricing Patterns
Pattern 1: Stable production
- 100% RI 3-year AURI
- Lowest cost for predictable workload
Pattern 2: Growing workload
- Compute SP 1-year (re-evaluate yearly)
- Some On-Demand for growth headroom
Pattern 3: Variable + batch
- Baseline: SP for steady state
- Peak: On-Demand
- Batch: Spot
Pattern 4: Serverless
- Lambda + Fargate covered by Compute SP
- Pay-per-execution savings on top
Câu hỏi ôn tập
-
Discount priority: RI applied trước hay sau SP?
Xem đáp án
RI applied trước, sau đó Savings Plans. Cả hai so sánh usage với committed resources: RI match exact instance type/AZ/OS configuration trước; Savings Plans flexible hơn và apply sau RI. Cả hai không thể "stack" trên cùng hour — RI committed hour không còn available cho SP. Unused RI/SP được "charged" dù không dùng — thiết kế để maximize utilization.
-
Convertible RI cho phép đổi gì?
Xem đáp án
Convertible RI cho phép exchange sang RI khác có equal or greater value: đổi instance family (m5 → r5), OS (Linux → Windows), tenancy (shared → dedicated), region, size. Không thể exchange xuống giá trị thấp hơn (phải exchange nhiều RI nhỏ lấy một RI lớn). AWS apply blended pricing khi exchange. Discount thấp hơn Standard RI (~54% vs ~72%) để bù đắp flexibility.
-
EC2 Instance SP khác Compute SP ở flexibility nào?
Xem đáp án
EC2 Instance SP: commit cho một instance family cụ thể trong một Region cụ thể (ví dụ: m5 in us-east-1) — có thể đổi size (m5.large → m5.4xlarge) và OS. Compute SP: flexible across instance family, size, Region, OS, và cả Lambda + Fargate. EC2 Instance SP discount cao hơn (~72%); Compute SP thấp hơn (~66%) nhưng flexible hơn nhiều. Compute SP phù hợp khi workload thay đổi.
-
Standard RI có thể sell on Marketplace không?
Xem đáp án
Có — Standard RI có thể bán lại trên AWS Reserved Instance Marketplace khi không còn cần. Điều kiện: không phải All-Upfront mới mua < 30 ngày, phải là 1-year RI còn ít nhất 1 tháng, không phải Windows/RHEL/SUSE với dedicated tenancy. Convertible RI không bán được trên Marketplace — đây là trade-off của flexibility. Giá bán do người bán set, AWS take 12% fee.
-
ODCR có discount không?
Xem đáp án
Không — On-Demand Capacity Reservation (ODCR) charge On-Demand rate kể cả khi không sử dụng. ODCR chỉ đảm bảo capacity available khi cần (không bị "capacity unavailable" errors). Để vừa có capacity reservation vừa discount, kết hợp với Zonal RI hoặc Savings Plans — chúng tự động apply discount lên ODCR matching. Hữu ích cho disaster recovery capacity reservation.
Bài tập thực hành
- Vào Cost Explorer → RI Recommendations
- So sánh cost 1 m5.xlarge với 5 pricing models trên Pricing Calculator
- Check RI utilization của account (nếu có)
- (Thử nghiệm) Mua 1 RI Zonal cho t3.micro 1-year No Upfront, observe sau
- Setup Compute SP 1-year $1/hr commitment (cancellable trong 7 days nếu thử)
Tài liệu tham khảo chính thức
Tiếp theo: Spot Instance Strategies