EFS vs FSx: When to Choose Which?
Learn the key differences between Amazon EFS and FSx and the optimal file storage selection criteria for different workloads.
Related Exam Domains
- Domain 3: Design High-Performing Architectures
Key Takeaway
EFS is for Linux/NFS-based shared file systems; FSx is for Windows (SMB) or high-performance (Lustre) workloads. Operating system and protocol requirements are the key selection criteria.
Exam Tip
Exam Essential: "Linux + NFS = EFS", "Windows + SMB = FSx for Windows", "HPC + Lustre = FSx for Lustre"
When Do You Need File Storage?
EBS is block storage attached to a single EC2 instance. But there are situations where multiple instances need simultaneous access to the same files:
- Sharing static content across a web server farm
- Persistent storage for container-based applications
- Sharing big data/ML training datasets
- Shared home directories or development environments
For these cases, you need shared file systems like EFS or FSx.
Key Differences Between EFS and FSx
Amazon EFS (Elastic File System)
- Protocol: NFS v4.0/4.1
- Operating System: Linux only
- Auto-scaling: Automatically scales to petabytes
- Availability: Multi-AZ by default
- Latency: ~10ms (General Purpose mode)
Amazon FSx Product Family
FSx offers 4 file system types:
| FSx Type | Protocol | Primary Use |
|---|---|---|
| FSx for Windows | SMB | Windows file server, AD integration |
| FSx for Lustre | Lustre | HPC, ML, video rendering |
| FSx for NetApp ONTAP | NFS, SMB, iSCSI | Hybrid cloud, multi-protocol |
| FSx for OpenZFS | NFS | ZFS-based Linux workloads |
EFS vs FSx: Detailed Comparison
| Aspect | EFS | FSx for Windows | FSx for Lustre |
|---|---|---|---|
| Protocol | NFS | SMB 2.0-3.1.1 | Lustre |
| OS | Linux | Windows, Linux | Linux |
| Max Throughput | 10+ GB/s | 2-12 GB/s | Hundreds of GB/s |
| Latency | ~10ms | ~1ms | Sub-millisecond |
| IOPS | Hundreds of thousands | Millions | Millions |
| S3 Integration | None | None | Native support |
| Active Directory | None | Native support | None |
| Auto-scaling | Yes | No (fixed size) | No (fixed size) |
When to Choose What?
Choose EFS When
-
Linux-based shared storage
- Shared file access from EC2, ECS, EKS, Lambda
- Static content for web server farms
-
Auto-scaling is needed
- Unpredictable storage capacity requirements
- Pay only for what you use
-
Serverless integration
- Lambda functions accessing file systems
- Persistent volumes for containers
Exam Tip
EFS + Lambda: Mount EFS in Lambda functions to load large ML models (bypass the 250MB package limit)
Choose FSx for Windows When
-
Windows workloads
- .NET applications
- SQL Server database files
-
Active Directory integration
- Enterprise user authentication
- Group policy-based access control
-
SMB protocol required
- Windows file shares
- DFS (Distributed File System) namespaces
Choose FSx for Lustre When
-
High Performance Computing (HPC)
- Hundreds of GB/s throughput needed
- Sub-millisecond latency
-
Machine Learning/Big Data
- Large training datasets
- SageMaker integration
-
Native S3 integration
- Access S3 data like a file system
- Automatically save processed results back to S3
Exam Tip
FSx for Lustre + S3: Link an S3 bucket to FSx for Lustre and S3 objects automatically appear in the file system. Changes can be exported back to S3.
Choose FSx for NetApp ONTAP When
-
Hybrid cloud
- Migration from on-premises NetApp
- NetApp SnapMirror replication
-
Multi-protocol access
- Access same data via NFS, SMB, iSCSI
- Mixed Windows and Linux environments
Understanding Performance Modes
EFS Performance Modes
| Mode | Characteristics | Suitable Workloads |
|---|---|---|
| General Purpose | Low latency, web serving | CMS, home directories |
| Max I/O | High throughput, higher latency | Big data, media processing |
EFS Throughput Modes
| Mode | Characteristics | Cost |
|---|---|---|
| Bursting | Proportional to storage size, credit-based | Included |
| Provisioned | Guaranteed fixed throughput | Additional fee |
| Elastic | Auto scales up/down | Usage-based |
Cost Optimization Strategies
EFS Cost Reduction
-
Lifecycle policies
- Files not accessed for 30+ days → Auto-move to IA class
- Up to 92% cost savings
-
One Zone option
- Suitable for dev/test environments
- 47% cheaper than Standard
FSx Cost Reduction
-
Data compression
- FSx for Windows, ONTAP: Automatic compression support
- Reduced actual storage capacity
-
Right-sizing
- FSx doesn't auto-scale
- Monitor usage and adjust size accordingly
SAA-C03 Exam Focus Points
- ✅ Protocol matching: "Need NFS → EFS", "Need SMB → FSx for Windows"
- ✅ Performance requirements: "Sub-millisecond latency, hundreds of GB/s → FSx for Lustre"
- ✅ S3 integration: "Process S3 data like files → FSx for Lustre"
- ✅ AD integration: "Active Directory + file shares → FSx for Windows"
- ✅ Auto-scaling: "Unpredictable capacity, auto-scaling → EFS"
Exam Tip
Sample Exam Question: "A group of Linux EC2 instances needs to share ML training data. The data is stored in S3 and sub-millisecond latency is required. Which storage should you use?" → Answer: FSx for Lustre (Native S3 integration + ultra-low latency)
Frequently Asked Questions
Q: Which is cheaper, EFS or FSx?
EFS Standard is $0.30/GB/month, FSx for Windows is $0.13/GB/month. However, FSx requires provisioning a fixed size, so EFS may be more economical if actual usage is low.
Q: Can I use EFS on Windows?
No. EFS only supports the NFS protocol, making it Linux-only. Use FSx for Windows for Windows workloads.
Q: Can I use FSx from Lambda?
Lambda can only directly mount EFS. To access FSx data, indirect access through EC2 is required.
Q: Is FSx for Lustre suitable for persistent data storage?
Scratch type is temporary storage with no data persistence. Persistent type supports Multi-AZ replication for permanent storage.
Q: Can I access EFS from on-premises?
Yes. You can access EFS via NFS from on-premises through AWS Direct Connect or VPN.