Object storage stores data as objects in flat buckets instead of files in folders or blocks on a disk. Because almost every provider speaks the Amazon S3 API, "S3-compatible storage" has become the standard way to keep backups, media and static files cheaply and at large scale.
Before you start
- No setup needed for this overview. For a hands-on example see back up a VPS to S3 with rclone.
How object storage works
- Bucket: a top-level container, e.g.
company-backups. - Object: the data plus metadata, addressed by a key such as
2025/10/db.sql.gz. Slashes only look like folders. - API: applications use HTTP requests (PUT, GET, DELETE, LIST), signed with an access key and secret key.
- Durability: providers replicate or erasure-code objects across disks and often across sites.
Object vs block vs file storage
| Object | Block | File | |
|---|---|---|---|
| Access | HTTP API | Raw disk attached to one server | Mounted share (NFS, SMB) |
| Scale | Virtually unlimited | Per volume | Per share |
| Edit in place | No, rewrite whole object | Yes | Yes |
| Best for | Backups, media, archives, static assets | OS disks, databases | Shared documents, home folders |
S3-compatible options
- Hosted: Amazon S3 and many other cloud providers offer S3-compatible object storage, often with cheaper egress or flat pricing. Compare storage, request and data transfer fees.
- Self-hosted: MinIO, Ceph's RADOS Gateway and Garage turn your own servers into S3 endpoints. See Ceph for virtualization.
Common uses
- Off-site backups for servers and websites (follow the 3-2-1 rule, see backups explained).
- User uploads and media for web apps, often served through a CDN.
- Static website hosting.
- Log and data archives with lifecycle rules that move old data to colder, cheaper tiers.
Security basics
- Keep buckets private by default; share with time-limited pre-signed URLs.
- Create access keys limited to one bucket with only the permissions needed.
- Enable versioning or object lock to protect backups from deletion and ransomware.
Frequently asked questions
Can I mount object storage as a drive?
Tools like rclone mount or s3fs can, but performance and file semantics differ from a real disk. Avoid running databases on it.
What does S3-compatible mean exactly?
The service accepts the same API calls as Amazon S3, so tools written for S3 work by changing the endpoint URL.
Is object storage cheaper than block storage?
Usually per GB, but watch request and egress charges.