Object Storage vs Block Storage: Which One Does Your App Need?
Block storage is a disk attached to one server; object storage is files over HTTP in a bucket. How EBS, S3, DigitalOcean Volumes and Spaces, and Linode storage differ, and how to choose between them.
Cloud providers sell storage in two main shapes. Block storage is a virtual disk you attach to a server, format with a filesystem, and treat like a local drive. Object storage is an HTTP service that stores files as named objects in buckets and returns them over the network. They solve different problems, are priced differently, and fail differently. This guide explains how each works, names the services on AWS, DigitalOcean, Linode, and other providers, and gives a practical rule for choosing between them.
Block storage: a disk for one server
Block storage presents raw blocks to an operating system. The server sees a device, puts a filesystem on it, and reads and writes through the kernel exactly as it would with a physical SSD. Because the operating system controls layout, block storage supports random reads and writes, file locking, permissions, and every application that expects a normal filesystem: databases, package managers, container runtimes, and the root disk of the server itself.
The constraints follow from the model. A volume is attached to one server at a time in one availability zone or region. Capacity is provisioned in advance and billed for the size you allocate, not the bytes you actually write. Performance is tied to the volume type and size, and moving a volume means detaching, snapshotting, or copying it.
Named services
On AWS the service is Amazon EBS, with several volume types ranging from general purpose SSD to provisioned IOPS and throughput-optimized HDD. DigitalOcean calls it Volumes Block Storage, attachable to Droplets in the same region. Linode offers Block Storage volumes for Linodes in the same data center. Hetzner Cloud Volumes attach to cloud servers in the same location, and Vultr, UpCloud, and Azure (Managed Disks) all follow the same pattern. Every one of them also gives each server a boot disk, which is block storage bundled with the instance.
Object storage: files over HTTP
Object storage has no filesystem and no server in the middle. You create a bucket, give it a globally unique name within the provider, and store objects in it by key. Each object is written whole and read whole; you cannot seek into the middle of an object and change a few bytes. Access is through an HTTP API, and most providers implement the Amazon S3 API so the same tools and libraries work across them.
The model removes most of block storage’s constraints. A bucket has no fixed size; you pay for the bytes stored plus requests and outbound data transfer. Any number of clients can read the same object at the same time from anywhere on the internet, subject to permissions. Durability is handled by the provider replicating objects across multiple devices and, on the hyperscalers, multiple facilities within a region. Objects can be versioned, given lifecycle rules that move them to colder storage tiers or delete them after a period, and served directly to browsers through a CDN.
Named services
Amazon S3 defined the category and its API. DigitalOcean Spaces is S3-compatible and includes a built-in CDN option. Linode Object Storage is likewise S3-compatible with per-region clusters. Hetzner Object Storage, Vultr Object Storage, and Google Cloud Storage all expose S3-style access; Azure Blob Storage uses its own API but plays the same role. Because the interfaces converge, code written against S3 usually needs only an endpoint and credential change to work elsewhere.
Side by side
| Characteristic | Block storage | Object storage |
|---|---|---|
| How it is accessed | As a disk attached to one server | Over HTTP from any client |
| Unit of work | Blocks; random read and write | Whole objects; write once, read many |
| Capacity | Provisioned size, billed whether used or not | Unlimited, billed per byte stored |
| Extra charges | Snapshots, IOPS on some tiers | Requests and outbound transfer |
| Sharing | One server at a time | Many readers and writers concurrently |
| Location | Bound to a zone or region | Regional, reachable from anywhere |
| Typical use | Databases, boot disks, application working sets | Uploads, media, backups, logs, static sites |
| AWS service | Amazon EBS | Amazon S3 |
| DigitalOcean service | Volumes | Spaces |
| Linode service | Block Storage | Object Storage |
Which one does your application need?
The deciding question is who needs to read and write the data and how. Apply these rules in order.
- If a process opens files with normal filesystem calls and expects to modify them in place, use block storage. PostgreSQL, MySQL, Redis persistence, Docker image layers, and the operating system itself all belong here.
- If the data is uploaded once and served many times, use object storage. User avatars, product images, video files, PDF exports, and static website assets are the classic cases. Serving them from a bucket keeps them off the application server’s disk and lets you add a CDN.
- If more than one server must see the same data, use object storage or a managed file service, not a block volume. A block volume attaches to one server. For shared POSIX access, providers offer network file services such as Amazon EFS, and DigitalOcean and Linode users typically run NFS on a Droplet or Linode or move the data to a bucket.
- If the data is a backup, put it in object storage. Even the backup of a block volume ends up as an object: EBS snapshots are stored in S3 behind the scenes, and a database dump belongs in a bucket with a lifecycle rule rather than on the same disk as the database.
- If cost per stored byte matters more than latency, choose object storage tiers. Infrequent access and archive classes on S3 and the equivalents elsewhere are priced for data you rarely read.
Practical details that catch people out
Block volumes cost money while attached to a stopped server. Stopping an instance on AWS, DigitalOcean, or Linode stops compute charges but the volume keeps billing. Delete volumes you no longer need, and check for orphaned volumes when you inventory an account.
Object storage charges for egress. Serving large files directly to the public from a bucket is convenient, but the outbound transfer line can exceed the storage line. Put a CDN in front, use the provider’s bundled transfer allowance where one exists, and watch the request count for workloads that read many small objects.
Bucket permissions are a security boundary. A bucket set to public exposes every object in it to the internet. Keep buckets private by default, grant access with IAM policies or scoped access keys, and use pre-signed URLs when a browser needs temporary access to one object. Every provider’s console warns about public buckets for a reason.
Block volume snapshots are point-in-time copies, not continuous backups. A snapshot taken while a database is writing may be inconsistent unless the database is quiesced or the filesystem is frozen first. For anything transactional, take an application-level dump as well.
Where to go next
Providers that pair block volumes with S3-compatible object storage in the same account are listed on the Buy DigitalOcean Accounts page and the Buy Linode Accounts page. For EBS, S3, and the full range of storage classes, see the Buy AWS Accounts page.
Related reading in the Cloud Library:
- A simple cloud backup strategy: snapshots, object storage, and retention
- Deploying your first cloud server: a practical checklist
- Cloud regions and availability zones: how to choose a location
Browse every guide in the Cloud Library, or compare the two developer clouds on the DigitalOcean vs Linode page.