Storage services: choosing the right one

The services at a glance

The Storage category of the exam covers seven services. Most questions come down to what kind of storage the workload needs (object, block, or file), who shares it, and how often it is read.

Service	Kind	Best for
Amazon S3	Object storage, Regional	Data lakeA central store for large amounts of structured and unstructured data kept in its original form, usually in Amazon S3, which many tools can analyze. AWS Lake Formation helps build and secure one.Glossary entry, backups, media, static website content, any data read and written as whole objects
Amazon S3 Glacier	Archive storage classes in S3	Long-term archives, from millisecond to 48-hour retrieval
Amazon EBS	Block storage for EC2, in one AZ (Availability Zone)An isolated location within an AWS Region, made up of one or more data centers with their own power, cooling, and networking. The AZs in a Region are linked by fast, low-latency connections, so spreading resources across them protects against the failure of one site.Glossary entry	Boot volumes, databases, and applications on one instance
Amazon EFS	File storage (NFS (Network File System)A protocol for sharing files over a network, used mostly by Linux and Unix systems. Amazon EFS, Amazon FSx for OpenZFS, and Amazon FSx for NetApp ONTAP provide NFS file systems.Glossary entry) for Linux, across Availability Zones	Shared files for many Linux instances, containers, and Lambda functions
Amazon FSx	Managed file systems: Windows File Server, Lustre, NetApp ONTAP, OpenZFS	Windows (SMB (Server Message Block)The file-sharing protocol used by Windows. Amazon FSx for Windows File Server and Amazon FSx for NetApp ONTAP provide SMB shares, and Amazon S3 File Gateway can present S3 buckets as SMB shares.Glossary entry) shares, HPC (High performance computing)Using many powerful computers together on large problems, such as simulations, genomics, or weather forecasting, often with fast networking between them. On AWS it uses EC2 instances with Elastic Fabric Adapter, AWS Batch, and AWS ParallelCluster.Glossary entry, multi-protocol or ZFS workloads
AWS Storage Gateway	Hybrid file, volume, and tape gateways	On-premisesIn data centers or offices that you run yourself, rather than in the cloud. Hybrid architectures connect on-premises systems to AWS, for example through AWS Direct Connect or a VPN.Glossary entry applications that use cloud storage through standard protocols
AWS Backup	Central backup service	Policy-based backups across AWS services and accounts

Object, block, or file?

Object (S3): whole objects over HTTPS (HTTP Secure)HTTP sent over a TLS-encrypted connection, so that requests and responses cannot be read or changed on the way, and the server proves its identity with a certificate.Glossary entry, unlimited scale, 11 nines of durability. Not a mounted disk, so not for a database's data files or an operating system.
Block (EBS): a network disk for an EC2 instance, replicated within one Availability Zone. Normally attached to one instance; Multi-Attach shares an io1 or io2 volume with up to 16 Nitro instances in the same Availability Zone. Instance store is temporary block storage on the host's own disks, for caches and scratch data.
File (EFS or FSx): a shared file system that many clients mount at once. EFS serves Linux clients over NFS and is Regional (across Availability Zones) by default; it doesn't support Windows instances. FSx gives you a specific file system: Windows File Server (SMB, Active Directory), Lustre (HPC and ML (Machine learning)Software that learns patterns from example data to make predictions or decisions, instead of following rules written by hand. A model is first trained on data, then used to make predictions on new data, which is called inference.Glossary entry, linked to S3), NetApp ONTAP (NFS, SMB, and iSCSI), or OpenZFS (NFS).

Hybrid and protection

Storage Gateway connects on-premises applications to AWS storage: NFS and SMB file shares backed by S3, iSCSI volumes, and virtual tapes archived to S3 Glacier Flexible Retrieval or Deep Archive. (FSx File Gateway, for FSx for Windows shares, is no longer available to new customers.)
AWS Backup centralizes and automates backups with backup plans across services such as EBS, EFS, FSx, RDS, DynamoDB, and S3, in the cloud and on premises.
For moving data in bulk, see the migration and transfer services.

Reverse mindmap: from the question to the service

Storage: which service?

Amazon S3
- Unlimited object storage, data lake leads to S3
- Unknown access pattern, automatic savings leads to S3 Intelligent-Tiering
- Static website assets leads to S3 behind CloudFront
S3 Glacier
- Cheapest archive, hours to restore leads to S3 Glacier Deep Archive
- Rarely read but needed in milliseconds leads to S3 Glacier Instant Retrieval
Amazon EBS
- Boot volume or database disk for one instance leads to EBS
- Highest IOPS for one database leads to EBS io2 Block Express
- Temporary scratch disk, lost with the instance leads to Instance store
File storage
- Shared POSIX file system for Linux across AZs leads to Amazon EFS
- Windows SMB shares with Active Directory leads to FSx for Windows File Server
- HPC or ML training on S3 data leads to FSx for Lustre
- NFS, SMB, and iSCSI from one system, or NetApp leads to FSx for NetApp ONTAP
Hybrid and backup
- On-premises apps writing files to S3 leads to S3 File Gateway
- Replace physical tape backups leads to Tape Gateway
- One backup policy for many services and accounts leads to AWS Backup

Commonly confused pairs

If the choice is between	Choose the first when	Choose the second when
S3 or EBS	Objects over an API (Application programming interface)A defined way for one program to ask another for data or actions, such as a set of HTTPS requests and responses. Every AWS service is controlled through its API, which the console, the CLI, and the SDKs call for you.Glossary entry, any scale, many readers	A mounted disk for one EC2 instance
EBS or EFS	One instance, lowest LatencyThe time between sending a request and receiving the response, usually measured in milliseconds. Distance and processing add to it; caching and serving users from nearby locations reduce it.Glossary entry block storage	Many Linux instances share files across AZs
EFS or FSx for Windows	Linux clients over NFS	Windows clients over SMB with Active Directory
EFS or FSx for Lustre	General shared files	HPC or ML needing very high throughput, often linked to S3
S3 Standard-IA or Glacier Instant Retrieval	Read about monthly	Read about quarterly, with a 90-day minimum
EBS snapshots or AWS Backup	Back up one service's volumes	One policy for many services, accounts, and AWS RegionA separate geographic area where AWS runs its services, such as us-east-1 in Northern Virginia, made up of several Availability Zones. Most resources live in one Region; you choose Regions for latency, data residency, and the services you need.Glossary entry

Key takeaways

Match the storage kind first: S3 for objects, EBS for one instance's disks, EFS or FSx for shared file systems.
EBS lives in one Availability Zone; S3 (except the One Zone classes) stores data in at least three, and EFS Regional file systems span several.
FSx comes in four types: Windows File Server, Lustre, NetApp ONTAP, and OpenZFS.
Storage Gateway brings AWS storage to on-premises applications; AWS Backup centralizes backup policies.