Understanding AWS EBS Storage Types

AWS Elastic Block Store (EBS) offers various types of volumes to provide flexible and scalable storage options for different applications. Among these, the st1 and sc1 volumes are designed for specific use cases that prioritize cost-efficiency and throughput.

Types of EBS Volumes

1. General Purpose SSD (gp3, gp2): Balanced price and performance for a wide variety of workloads.
2. Provisioned IOPS SSD (io2, io1): Designed for mission-critical applications requiring very high IO performance.
3. Throughput Optimized HDD (st1): Cost-effective storage for frequently accessed, throughput-intensive workloads.
4. Cold HDD (sc1): Lowest cost option designed for less frequently accessed data.

Why st1 and sc1 Volumes Aren't Suitable for Root Volumes

Considerations with st1 and sc1 Volumes

When you create an instance, the root volume contains the operating system and plays a critical role in the instance's performance. Here are some technical reasons why st1 and sc1 volumes are not suitable for root volumes:

1. I/O Performance Characteristics:
   • Root volumes require consistent I/O performance to ensure the operating system boots efficiently. st1 and sc1 volumes are HDD-based and optimized for sequential I/O operations that provide a different performance profile.
   • st1 offers a baseline throughput performance of 40 MB/s per TB with a burst capability, while sc1 offers even lower throughput at 12 MB/s per TB.
2. Latency:
   • st1 and sc1 have higher latencies compared to SSD-based volumes (gp3, gp2, io2, io1) which are crucial for operating system-level operations.
3. Volume Durability:
   • While EBS volumes are inherently designed with redundancy, the underlying technology of st1 and sc1 is primarily optimized for cost and throughput rather than resilience in high-demand runtime environments typical for OS drives.
4. Use Case Alignment:
   • st1 is ideal for workloads such as big data, data warehouses, and log processing. sc1 is better reserved for workloads that are rarely accessed and require the lowest cost storage. Neither aligns with typical root volume operations that demand fast, consistent performance.

AWS Recommendations

AWS typically recommends using SSD-based EBS volumes like `gp2`, `gp3`, or `io2` for root volumes due to their lower latency and steady performance irrespective of the workload.

Summary Table of EBS Volume Characteristics

Examples of Technical Use Cases

1. st1 Volume Use Case:
   • A data analytics company processing batch jobs overnight might utilize st1 volumes to manage the data ingestion and transformation due to the large, sequential throughput requirements.
2. sc1 Volume Use Case:
   • An organization storing archival data like old log files might choose sc1 volumes for cost savings since access is infrequent, and performance demand is minimal.

Conclusion

In sum, while AWS offers st1 and sc1 volumes for cost-effective and throughput-intensive applications, they do not meet the performance and latency demands required of a root volume. Organizations seeking optimal performance for their root volumes should leverage SSD-based options that align with the high I/O demand and reliability required for operating system operations. Choosing the correct volume type is pivotal in ensuring your infrastructure runs smoothly and efficiently, aligning to your workload's specific needs.

By understanding the distinct capabilities and limitations of each AWS EBS volume type, architects and engineers can make informed decisions aligning infrastructure to workload requirements.