🔹 1. What is an EBS-Backed Instance?
- An EBS-backed instance = an EC2 instance whose root volume (boot disk) is stored on Amazon EBS (Elastic Block Store).
- EBS = network-attached block storage.
- The root volume lives outside the physical host → it persists even if the instance is stopped/terminated (unless you set Delete on Termination).
✅ Features of EBS-backed instances:
- Start up quickly.
- Root volume size can be changed.
- Can stop and restart the instance (state preserved).
- Snapshots possible (backup to S3).
🔹 3. Key Differences
| Feature | EBS-Backed | Instance Store-Backed |
|---|---|---|
| Persistence | Data survives stop/start (unless deleted) | Data lost when instance stops/terminates |
| Stop/Start | Allowed | Not supported (must terminate) |
| Size | Flexible, resizable | Fixed size tied to instance type |
| Snapshots | Yes (via EBS → S3) | No |
| Performance | Network-attached (good, consistent) | Physically-attached (very fast) |
| Use case | Databases, apps, long-term workloads | Caching, scratch space, temporary workloads |
🔹 4. Today’s Reality
- Most EC2 instances are EBS-backed by default.
- Instance store-backed AMIs exist but are rare and typically used in specialized, high-performance workloads (e.g., HPC, caching).
✅ In short:
- EBS-backed instance → boot volume stored on EBS (persistent, flexible, common).
- Instance store-backed instance → boot volume on ephemeral local disk (fast, temporary, less common today).
🔹 Why use Instance Store?
- Ultra-fast local storage 🚀
- Instance store = disks physically attached to the EC2 host.
- Way faster IOPS/throughput than network-attached EBS.
- Useful for caching, scratch space, or temporary high-speed processing.
- Temporary data needs 🗑️
- Example: Processing a video file, generating intermediate results, then uploading the final version to S3.
- If the instance stops/terminates, you don’t care if the scratch data is lost.
- Included with some instance families 💡
- Some instance types (like
i3,d2,h1) come with instance store as part of the package. - Since it’s included, you might use it for local cache/buffers without extra EBS cost.
🔹 Why NOT use Instance Store?
- Data loss: Gone if instance stops, hibernates, or fails.
- No snapshots: You can’t back it up to S3 like EBS.
- Not resizable: Tied to instance type.
🔹 Cost Perspective
- Instance store volumes themselves aren’t directly billed like EBS.
- But they’re only available on certain (often specialized, more expensive) instance families.
- So they’re not used to save money, rather they’re used for performance or because the instance type already includes them.
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