💾 EBS vs EFS vs S3 — How Does Your App See the Storage?
EBS — Elastic Block Store
Acts like a hard drive plugged into your EC2 instance. One instance, one AZ. Your OS formats and mounts it. Data persists after stop.
🧠 Think: "My server's hard drive"
EFS — Elastic File System
Acts like a shared network drive. Multiple EC2 instances across multiple AZs can mount it simultaneously. Auto-scales, no capacity to manage.
🧠 Think: "Shared folder that all my servers can access"
S3 — Simple Storage Service
Not a file system — an object store. You don't mount it, you call an API (PUT, GET). Flat blobs with URL keys. Massive scale, globally accessible, cheap.
🧠 Think: "A giant bucket of files accessible over the internet"
| 📋 Quick pick |
|---|
| Temp files on one server → EBS · Shared config files across servers → EFS · User photos accessible anywhere → S3 |
⚡ Instance Store — The One Everyone Forgets (And It's the Fastest)
Every EC2 host machine has real physical disks attached to it. Instance Store lets your instance use those disks directly — no network hop, just raw disk. EBS feels local but still goes over the network. That's why Instance Store wins on speed.
The catch: data only exists while the instance runs. Stop it, terminate it, or if the hardware fails — gone. Not a debate, just gone.
It's included in the EC2 instance price — no extra charge.
| 📋 Exam trigger words |
|---|
| "fault-tolerant" · "can handle failures" · "distributed architecture" · "highest I/O performance" · "lowest latency storage" → Instance Store |
Data Protection, Migration & Storage Services
| Service | Does what | Analogy | Trigger words |
|---|---|---|---|
| AWS Backup | Centralized automated backups across ALL AWS services and on-premises | The automated backup janitor who never forgets | "centralize backups" "automate backup policy" "across services" |
| Elastic Disaster Recovery | Continuously replicates live servers for rapid failover | The understudy ready to go on stage instantly | "disaster recovery" "minimal data loss" "failover" "RPO/RTO" |
| DataSync | Transfers and migrates data between storage systems | The moving truck for your data | "migrate data" "transfer to AWS" "sync on-premises to S3" |
| Storage Gateway | Lets on-premises systems use AWS storage as if it were local | The magic portal that makes cloud look local | "hybrid storage" "on-premises access to cloud" "replace tape backups" |
| Snowball Edge | Physical device for massive data transfer when network is impractical | The armored truck when the internet highway is too slow | "terabytes to petabytes" "physical transfer" "no internet" "rugged" |
Storage Gateway — Three Flavors
| Flavor | Presents as | Stores to | Use when |
|---|---|---|---|
| File Gateway | NFS/SMB network file share | S3 | Replace on-premises file servers |
| Volume Gateway | iSCSI block storage | S3 + EBS snapshots | Back up on-premises block storage |
| Tape Gateway | Virtual tape library | S3 / Glacier | Replace physical tape backup infrastructure |
The Storage Gateway mental model:
Your on-premises servers think they're writing to local storage.
They're actually writing to AWS.
The gateway handles the translation invisibly.
Key Distinctions
| Question | Answer |
|---|---|
| Need to back up AWS resources centrally? | AWS Backup |
| Need servers to keep running if disaster hits? | Elastic Disaster Recovery |
| Need to move data to AWS once or regularly? | DataSync |
| Need on-premises servers to use AWS storage daily? | Storage Gateway |
| No internet, massive data, physical shipment? | Snowball Edge |
The trap: Elastic Disaster Recovery sounds like backup — it's not.
It replicates LIVE systems for failover, not periodic backup copies.
Reserved vs Dedicated — Completely Different Concepts
Reserved = a PRICING decision
You commit to 1 or 3 years → AWS gives you up to 72% discount.
Hardware is still shared with other AWS customers.
Dedicated = a HARDWARE decision
You get physically isolated servers.
Other AWS customers cannot run workloads on your hardware.
Exists for compliance requirements and software licensing.
They are independent — you can mix and match:
| Combination | Means |
|---|---|
| Reserved + Shared hardware | Normal Reserved Instance — discount only |
| Reserved + Dedicated hardware | Commit AND get physical isolation |
| On-Demand + Dedicated hardware | Dedicated Instance/Host, no commitment |
Dedicated Instance vs Dedicated Host
| Dedicated Instance | Dedicated Host | |
|---|---|---|
| Hardware dedicated to you | ✅ | ✅ |
| You know WHICH server you're on | ❌ AWS picks | ✅ You choose |
| Visibility into sockets/cores | ❌ | ✅ |
| Bring your own license (BYOL) | ❌ | ✅ |
| Cost | Lower | Higher |
| Use when | Need dedicated hardware for compliance | Need specific server for BYOL licensing |
The one sentence: Reserved = discount for commitment.
Dedicated = physical isolation for compliance or licensing.
You can mix and match them.
Exam trigger: "existing server-bound software licenses" + "compliance" → Dedicated Host
Exam trigger: "dedicated hardware" without licensing mention → Dedicated Instance
Trigger: "existing server-bound software licenses" + "compliance" → Dedicated Host
EC2 Instance Purchasing Decision Tree
| Scenario | Choose |
|---|---|
| Short term, uninterruptible | On-Demand |
| Long term 1-3 years, predictable | Reserved |
| Fault-tolerant, can be interrupted | Spot |
| Dedicated hardware, BYOL licensing | Dedicated Host |
| Dedicated hardware, compliance only | Dedicated Instance |
EC2 Launch Requirements
| Required | Optional |
|---|---|
| Security Group | Elastic IP |
| VPC and Subnet | Key pair (if no other access method) |
| EBS Root Volume | Additional EBS volumes |
| AMI | Instance store volumes |
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