Introduction
Object storage, block storage, and VM disk are three different ways to store data in cloud infrastructure, and each is optimized for a different access pattern. If you choose the wrong one, you can end up with avoidable performance bottlenecks, higher costs, or an architecture that becomes difficult to scale later.
For teams deploying on Raff, this decision matters because storage is not just a capacity question. It affects how your application reads and writes data, how you handle backups, how easily you scale, and how tightly your data is coupled to a virtual machine. In practice, the right choice depends less on raw size and more on how the data behaves.
This guide explains what each storage model is, how it works, and when to use it. You will learn the strengths and trade-offs of object storage, block storage, and VM disk, how to match them to real workloads, and how to build a practical storage strategy for cloud applications.
Understanding the Three Storage Models
At a high level, cloud storage can be divided into three common layers:
| Storage type | Best for | Access method | Typical examples |
|---|---|---|---|
| VM disk | OS, local app files, tightly coupled workloads | Local filesystem on the VM | /, /var, packages, local temp files |
| Block storage | Databases, persistent app data, mounted filesystems | Attached volume mounted as a disk | PostgreSQL data, uploads, application storage |
| Object storage | Static assets, backups, media, logs, archives | API-based object access | Images, videos, backups, artifacts |
These categories may sound similar at first because all three can store data, but they behave very differently in production.
What VM disk means
VM disk is the storage included with the virtual machine itself. It holds the operating system, installed packages, configuration files, logs, and whatever local files your applications use by default.
This storage is simple because it is already there when the VM is created. If you install Ubuntu, deploy Nginx, and run an application, you will almost always start with the base VM disk.
VM disk works well for:
- Operating system files
- Local configuration
- Small single-server applications
- Temporary or low-value local data
- Early-stage prototypes
The main limitation is coupling. If your application data lives only on the VM disk, that data is tightly tied to that server’s lifecycle. That may be acceptable for small workloads, but it becomes less attractive once the system needs cleaner persistence or growth.
What block storage means
Block storage is network-attached storage that behaves like a raw disk. You attach it to a VM, format it with a filesystem, and mount it at a path such as /mnt/data or /var/lib/postgresql.
From the operating system’s perspective, block storage looks like another disk. That makes it ideal for applications that expect standard filesystem semantics, such as databases, content management systems, and persistent application data.
Block storage is a good fit for:
- Database data directories
- Persistent application uploads
- Large mounted filesystems
- Workloads that may need more storage later
- Data that should remain somewhat independent from the base VM
Because block storage is separate from the VM’s included disk, it gives you more flexibility in how you grow and manage persistent data.
What object storage means
Object storage stores data as discrete objects accessed over an API instead of a mounted disk. Each object has data, metadata, and an identifier. Rather than editing files in place on a mounted filesystem, applications upload and retrieve objects via API calls.
Object storage is ideal for large-scale unstructured data and content that does not require low-level filesystem behavior.
Typical object storage use cases include:
- Backups and archives
- Images and video
- Static website assets
- Build artifacts
- Log exports
- Documents and downloads
Object storage is usually the most scalable and durable choice for file-like content that does not belong inside a database or local application disk.
Why the Differences Matter
The reason these storage types matter is that applications do not simply need “space.” They need the right kind of space.
A PostgreSQL server needs low-latency, filesystem-based storage. A backup archive needs durable, scalable storage with low operational overhead. Your operating system needs a root disk to boot and run services. Those are different requirements, so they should not always live in the same place.
The most common storage mistake is forcing one storage model to handle every workload. That usually shows up as one of these patterns:
- Keeping database data on the same small VM disk as the OS
- Storing large media libraries inside application directories on the root disk
- Using object storage for workloads that need direct block-level filesystem behavior
- Treating local disk as a long-term storage plan for a service that needs independent scaling
A better approach is to choose storage based on access pattern, not convenience.
Comparing Performance, Durability, and Scaling
Performance
Performance is not just about raw speed. It is about matching the storage model to the application’s expectations.
VM disk is often fast and simple for local reads and writes, especially for small workloads. It is the default option for booting the system and running lightweight services.
Block storage is generally the stronger choice when you need persistent filesystem performance for stateful services such as databases. It behaves like a proper disk and supports filesystems, which makes it a practical option for many production application workloads.
Object storage is not designed to replace a mounted disk for transactional workloads. It works best when applications upload or fetch discrete objects rather than perform frequent low-level file operations.
Durability
Durability depends on both architecture and operations.
VM disk may be perfectly acceptable for system files and small deployments, but it is often not the ideal long-term home for important application data because it is closely tied to the VM itself.
Block storage improves durability strategy by separating persistent data from the base server disk. It is still your responsibility to protect that data with snapshots, backups, and sound architecture.
Object storage is usually the most natural fit for durable content storage, especially for backups, archives, and static assets that need to exist independently of any one compute node.
Scaling
Scaling characteristics also differ:
| Question | VM disk | Block storage | Object storage |
|---|---|---|---|
| Good for OS and local app files? | Yes | Sometimes | No |
| Good for database storage? | Limited | Yes | No |
| Good for backups and archives? | No | Sometimes | Yes |
| Easy to use with APIs and apps? | Limited | Limited | Yes |
| Best for large static assets? | No | Sometimes | Yes |
| Tied closely to one VM? | Yes | Less so | No |
If you expect the data footprint to grow independently from compute, block storage or object storage usually becomes the better long-term choice.
How to Choose the Right Storage for Common Workloads
Websites and small web apps
For a simple website or small app, VM disk may be enough at first. Your OS, web server, and app can all run on the included disk. But as soon as you add user uploads, media, or a growing database, you should reconsider that layout.
A practical evolution looks like this:
- VM disk for the OS and app runtime
- Block storage for persistent app data or the database
- Object storage for media, backups, or static file delivery
Databases
Databases usually belong on block storage or carefully planned persistent storage, not in object storage. They rely on filesystem semantics, low-latency access, and predictable write behavior.
You can run a small database on a VM disk early on, but once the workload becomes production-critical, separate persistent storage is usually a more disciplined approach.
Backups and archives
Backups are one of the clearest object storage use cases. They need to be durable, scalable, and independent from the VM that generated them. Backup data usually does not need to behave like a mounted filesystem. It needs to be retained, organized, and restored when necessary.
User uploads and media
If users upload images, documents, or videos, object storage is often the right target. It prevents media growth from crowding the root disk and gives the application a cleaner separation between compute and asset storage.
Logs and artifacts
Logs that need long retention, exported reports, CI artifacts, and generated assets are also strong object storage candidates. Keeping them off the application root disk reduces clutter and simplifies scaling.
Best Practices for Storage Design
Use VM disk for what belongs to the server itself
Your operating system, local packages, temporary files, and tightly coupled runtime data belong on the VM disk. This keeps the base system simple and predictable.
Use block storage for persistent mounted data
If an application expects a normal filesystem and the data should outlive routine VM changes, block storage is usually the better fit.
Use object storage for file-like content at scale
If the data is static, unstructured, or best accessed over an API, object storage is often the cleanest design choice.
Do not store everything in one place
A mature architecture usually uses more than one storage model. That is not unnecessary complexity. It is a sign that the system is matching data to the right persistence layer.
Design backup strategy separately from primary storage
Primary storage and backup storage are not the same thing. Even if your data is on block storage, your backup plan may still involve snapshots, scheduled backups, and external object-based retention.
Raff-Specific Context
Raff’s public platform already emphasizes several storage-adjacent building blocks that fit this decision framework well. Raff offers Linux VMs, block storage volumes, snapshots, automated backups, and a listed object storage product path, which means the platform already maps cleanly to the three-layer storage conversation of compute disk, attached persistent storage, and object-style storage services. :contentReference[oaicite:2]{index=2}
In practical terms, a Raff deployment might look like this:
- A Linux VM for the operating system and application runtime
- A block storage volume for database or persistent app data
- Snapshots and backups for recovery planning
- Object storage for media, archives, and exported data as the architecture matures
That model is especially useful for developers and growing teams because it lets you start simply and introduce separation only where it adds real value.
Conclusion
Object storage, block storage, and VM disk are not competing versions of the same tool. They solve different problems.
Use VM disk for the server itself and tightly coupled local workloads. Use block storage for persistent filesystem-based application data, especially for databases and mounted storage. Use object storage for backups, static assets, archives, and large unstructured datasets that need API-based access and independent scaling.
If you make storage decisions based on how data is accessed rather than where it is easiest to put it today, your architecture will be easier to scale, protect, and operate over time.
For next steps, pair this topic with /learn/guides/block-storage-vs-local-disk, /learn/guides/cloud-server-backup-strategies, and Raff’s storage-related product pages such as /products/volumes and /products/object-storage.