Shared file storage appears in 51+ questions across SAA-C03 and SOA-C03. The exam tests when to use EFS (Linux NFS), which FSx variant (Windows/Lustre/ONTAP/OpenZFS), and performance class selection. This post covers the complete decision framework.
Serverless, elastic
Multi-AZ by default
Lambda compatible
Lifecycle tiering
NTFS, AD integration
DFS namespaces
Shadow copies
Multi-AZ HA
Sub-millisecond latency
100s GB/s throughput
S3-linked (lazy load)
Scratch or persistent
NFS + SMB + iSCSI
NetApp features
Snapshots, cloning
Compression, dedup
Detailed Comparison
| Feature | EFS | FSx Windows | FSx Lustre | FSx ONTAP |
|---|---|---|---|---|
| Protocol | NFSv4 | SMB | POSIX (Lustre) | NFS, SMB, iSCSI |
| OS | Linux | Windows | Linux | Linux + Windows |
| Capacity | Elastic (auto-grows) | Provisioned (32GB-64TB) | Provisioned (1.2TB-PBs) | Provisioned (auto-grows with tiering) |
| Throughput | Up to 10+ GB/s (Elastic) | Up to 2 GB/s | 100s GB/s | Up to 4 GB/s |
| Latency | Low milliseconds | Sub-millisecond (SSD) | Sub-millisecond | Sub-millisecond (SSD tier) |
| HA | Multi-AZ (Regional) or One Zone | Multi-AZ or Single-AZ | Single-AZ (Persistent or Scratch) | Multi-AZ |
| S3 integration | No native link | No | Yes (S3-linked, lazy load) | No native link |
| Best for | Web serving, CMS, containers, Lambda | .NET apps, SQL Server, Windows workloads | HPC, ML training, video processing | Multi-protocol, NetApp migration, DevOps |
EFS Performance Classes
| Mode | Throughput | Use Case |
|---|---|---|
| General Purpose | Lowest latency (default) | Web serving, CMS, home directories |
| Max I/O | Higher aggregate throughput (higher latency) | Big data, media processing, highly parallel (legacy — use Elastic) |
| Elastic Throughput | Auto-scales up to 10+ GB/s (pay per use) | Spiky workloads, unknown patterns (recommended for most) |
| Provisioned Throughput | Fixed throughput regardless of data size | Small datasets needing high throughput (predictable) |
EFS Storage Classes & Lifecycle
- Standard: Frequently accessed data. Multi-AZ durability.
- Infrequent Access (IA): 92% cheaper storage, per-access retrieval fee. Auto-tiered via lifecycle policy.
- One Zone: Single-AZ (20% cheaper than Standard). Good for dev/test or data that can be recreated.
- One Zone-IA: Cheapest option. Single AZ + infrequent access pricing.
- Lifecycle policy: Move files to IA after 7/14/30/60/90 days of no access. Can transition back on access.
FSx for Lustre — S3 Integration
- S3-linked: FSx Lustre filesystem linked to S3 bucket. Data lazy-loaded on first access.
- Scratch: Temporary, no replication. Highest performance. Use for short-term processing (ML training job).
- Persistent: Data replicated within AZ. Use for longer-term workloads needing durability.
- Write-back: Modified files automatically exported back to S3.
- Pattern: S3 (durable storage) → FSx Lustre (high-performance processing) → results back to S3
Exam Tips
| Exam | Key Points |
|---|---|
| SAA-C03 | “Linux shared file system” → EFS. “Windows file share with AD” → FSx for Windows. “HPC/ML high throughput” → FSx for Lustre. “Multi-protocol (NFS+SMB)” → FSx ONTAP. “Lambda needs shared storage” → EFS (only file system Lambda supports). “Reduce storage costs” → EFS lifecycle to IA. “S3 data for HPC processing” → FSx Lustre linked to S3. “Auto-growing” → EFS (elastic). “Migrate NetApp” → FSx ONTAP. |
AWS Certification Exam Practice Questions
Question 1:
A company runs a content management system on multiple EC2 Linux instances behind an ALB. The instances need shared access to uploaded media files. The storage must auto-scale as content grows and support Multi-AZ for high availability. Which storage solution fits?
- Amazon EBS with Multi-Attach enabled
- Amazon EFS with Standard storage class (Regional)
- Amazon S3 with s3fs mount on each instance
- FSx for Lustre linked to an S3 bucket
Show Answer
Answer: B — EFS provides a shared NFS file system accessible from multiple EC2 instances simultaneously. Standard (Regional) storage class stores data redundantly across multiple AZs. Capacity auto-scales. EBS Multi-Attach (A) only works within a single AZ and requires cluster-aware applications. S3 (C) isn’t a POSIX file system. FSx Lustre (D) is overkill for a CMS.
Question 2:
A machine learning team needs to train models on a 10TB dataset stored in S3. Training jobs require sub-millisecond read latency and 50+ GB/s aggregate throughput across hundreds of GPU instances. Training runs last 3-4 hours. Which storage is optimal?
- EFS with Elastic Throughput mode
- FSx for Lustre (Scratch) linked to the S3 bucket
- EBS gp3 volumes attached to each instance with data copied from S3
- FSx for Windows File Server with SSD storage
Show Answer
Answer: B — FSx for Lustre provides sub-millisecond latency and hundreds of GB/s throughput — designed for HPC/ML. S3-linked means data is lazy-loaded from S3 on first access (no pre-copy needed). Scratch type is perfect for short training jobs (no replication needed, highest performance, cheapest). After training, results write back to S3. EFS (A) maxes at ~10 GB/s. EBS (C) requires copying to each instance individually.
Question 3:
A company is migrating their Windows file server to AWS. The file server uses NTFS permissions, DFS namespaces, and integrates with their Active Directory for access control. Which AWS service provides native support for all these features?
- Amazon EFS with POSIX permissions mapped to Windows
- Amazon FSx for Windows File Server with Active Directory integration
- Amazon S3 with IAM policies mimicking NTFS permissions
- FSx for ONTAP with SMB protocol
Show Answer
Answer: B — FSx for Windows is built on Windows Server and natively supports NTFS permissions, DFS namespaces, DFS replication, shadow copies, and Active Directory integration. It’s a drop-in replacement for on-premises Windows file servers. EFS (A) is NFS/Linux only. ONTAP (D) supports SMB but doesn’t have native Windows features like DFS namespaces.
Question 4:
A company stores 50TB in EFS but only 5TB is accessed regularly. They want to reduce costs without changing application behavior or access patterns. Which approach achieves the highest cost reduction?
- Switch to EFS One Zone storage class
- Enable EFS Intelligent-Tiering lifecycle policy — automatically moves files not accessed for 14 days to Infrequent Access (IA) storage class
- Move the entire EFS to S3 and use File Gateway
- Migrate to FSx for Lustre which is cheaper at scale
Show Answer
Answer: B — EFS lifecycle policy automatically transitions files not accessed for N days to IA class (92% cheaper per GB). Since only 5TB of 50TB is active, 45TB moves to IA — saving ~90% on that 45TB with zero application changes. Files automatically move back to Standard when accessed. One Zone (A) saves 20% but loses Multi-AZ resilience. S3 (C) requires application changes.
Question 5:
A company needs shared file storage accessible from both Linux and Windows instances simultaneously. They also need snapshot capabilities and data compression to reduce storage costs. Which service supports all requirements?
- EFS (supports Linux) + FSx for Windows (supports Windows) — two separate systems
- FSx for ONTAP — supports NFS (Linux), SMB (Windows), snapshots, and inline compression/deduplication
- S3 with separate mount tools for Linux and Windows
- EBS Multi-Attach with a cluster file system
Show Answer
Answer: B — FSx for ONTAP is the only AWS file service supporting NFS (Linux) + SMB (Windows) simultaneously on the same data. It also includes NetApp features: snapshots, FlexClone (instant copies), inline compression, and deduplication. Perfect for mixed-OS environments. Two separate systems (A) don’t share the same data. S3 (C) isn’t a file system.
Related Posts
- Storage Gateway vs DataSync vs Snow
- S3 vs EBS vs EFS Compared
- Three-Tier Web Architecture
- Container Platform Architecture
References
- Amazon EFS User Guide
- FSx for Windows File Server Guide
- FSx for Lustre Guide
- Choosing the Right File System — AWS Blog
Frequently Asked Questions
EFS vs FSx for ONTAP — both support NFS. Which should I choose?
EFS: Simpler, serverless (no capacity planning), auto-scales, cheaper for large elastic workloads, native Lambda support. FSx ONTAP: Multi-protocol (NFS+SMB+iSCSI), compression/dedup, NetApp features (FlexClone, SnapMirror), better for hybrid/on-prem integration. Choose EFS for pure Linux NFS with auto-scaling needs. Choose ONTAP when you need multi-protocol, compression, or NetApp-compatible features.
When is FSx for Lustre better than EFS?
When you need extreme throughput (100s GB/s) and sub-millisecond latency for parallel workloads: ML training, HPC simulations, video rendering. Also when data lives in S3 and you need a high-performance processing layer on top (S3-linked Lustre). EFS maxes at ~10 GB/s and has millisecond latency — fine for web/general purpose, not enough for HPC.