Block Storage and Object Storage: Choosing Correctly

These two are not competing options for the same job. They solve different problems, and most storage difficulties come from using one where the other belongs.

Block storage

A virtual disk attached to one machine. You format it, mount it and use it like any drive. Applications read and write files without knowing anything unusual is happening.

Suited to: databases, application working directories, anything expecting ordinary filesystem behaviour, and anything needing low-latency random access.

Limits: normally attached to one machine at a time, sized in advance, and billed for the size provisioned rather than the space used.

Object storage

A key-value store accessed over HTTP. You put an object under a key and get it back by that key. There is no filesystem, no partial write, and no directory in the real sense.

Suited to: user uploads, images and video, backups, logs, static assets, and anything many clients or machines read simultaneously.

Limits: higher latency per operation than a local disk, no in-place modification of part of an object, and eventual consistency on some operations depending on the provider.

The decision in one line

If one machine needs it as a filesystem, use block. If many clients need it over the network, use object.

Common mistakes

Storing uploads on the application server’s disk

Works perfectly with one server and breaks the moment there are two, because half the requests find the file missing. It also ties user data to a machine you wanted to treat as replaceable. Object storage solves both.

Running a database on object storage

Databases need low-latency random access and partial writes. Object storage provides neither.

Treating object storage as a filesystem

Listing a bucket with a million keys to find one file is slow and sometimes expensive. Store the key in your database and fetch it directly.

Cost shapes differ

Block storage bills for provisioned capacity whether used or not, which is why detached volumes are a classic silent cost. Object storage typically bills for data stored plus requests plus egress, so a bucket serving heavy public traffic can cost more in transfer than in storage. See bandwidth, egress and the cost of moving data.

Where performance matters most

For block storage, latency is frequently the real constraint on database throughput, which is why providers emphasising storage performance such as UpCloud are chosen for write-heavy workloads.