Amazon EBS (Elastic Block Store)
Amazon Elastic Block Store (EBS) provides block level storage volumes for use with EC2 instances. EBS volumes behave like raw, unformatted block devices. You can mount these volumes as devices on your instances.
Volume Types
Solid State Drives (SSD) - Performance
- General Purpose SSD (gp2 / gp3):
- Balanced price/performance.
- gp3: Baseline 3,000 IOPS and 125 MB/s throughput regardless of size. Can scale IOPS/Throughput independently.
- gp2: Performance linked to volume size. Burst capabilities.
- Use Case: Boot volumes, low-latency apps, Dev/Test.
- Provisioned IOPS SSD (io1 / io2 Block Express):
- Highest performance. Sustained IOPS.
- io2: Higher durability (99.999%).
- Multi-Attach: Attach one volume to multiple EC2 instances (io1/io2 only).
- Use Case: Critical databases (Mission-critical), high-throughput workloads.
Hard Disk Drives (HDD) - Capacity
- Throughput Optimized HDD (st1):
- Low cost, designed for frequently accessed, throughput-intensive workloads.
- Use Case: Big Data, Data Warehousing, Log processing.
- Cannot be a Boot Volume.
- Cold HDD (sc1):
- Lowest cost HDD. Infrequently accessed data.
- Use Case: File servers, Archive.
- Cannot be a Boot Volume.
Key Features
- Availability Zone Bound: An EBS volume is created in a specific AZ and is automatically replicated within that AZ. It cannot bridge AZs. To move to another AZ, you must snapshot and restore.
- Snapshots: Point-in-time backups stored in S3.
- Incremental (only improved blocks are saved).
- Encrypted snapshots create encrypted volumes.
- Elastic Volumes: You can modify volume type, size, and IOPS on the fly without detaching the volume.
- Encryption: Seamless encryption of data at rest and in transit using KMS.
Exam Tips
- Instance Store vs EBS:
- Instance Store: Ephemeral (data lost on stop/terminate). High performance (physically attached).
- EBS: Persistent (data retained on stop). Network attached.
- "High throughput / Big Data": Think st1.
- "Mission Critical DB / High IOPS": Think io1/io2.
- Delete on Termination: By default, the Root volume is deleted when the instance terminates, but extra attached volumes are NOT.
Common Use Cases
- OS Boot volumes (SSD).
- Database storage (SSD).
- Big Data analytics engines (HDD).