# Virtual Machines vs Containers - What Actually Matters


Ever wondered why container technologies like Docker took over the development world so quickly? Let's break down the real differences between traditional VMs and containers - and why you might want to use one over the other.

## Key Distinctions

**Containers** are like lightweight packages that contain just your app and what it needs to run, sharing resources with your main system.

**Virtual Machines** are like having a whole computer inside your computer. Complete with its own operating system, memory, and everything else.

### Why Developers Love Containers

#### They're Fast
- Start up in seconds (not minutes)
- Take up way less space
- You can run many more of them on the same hardware

#### They're Consistent
- Works on your machine? Will work on everyone's machine
- No more "but it works locally" problems
- Same environment from development to production

#### They're Simple
- Easy to share with your team
- Quick to update and modify
- Less configuration headaches

### When VMs Still Make Sense

Sometimes you actually want a full computer-within-a-computer:

- You need to run a completely different operating system
- You're dealing with legacy applications that need specific system configurations
- You require maximum isolation for security reasons

### Real-World Comparison

Think of it like this:
- **Containers** are like apartments in a well-managed building (shared infrastructure, efficient, but with some limitations)
- **VMs** are like having your own house (complete control, but with more overhead)

## Containers and VMs in Zerops

### Why Zerops Uses Both

At Zerops, we use **containers** as our primary runtime environment - they're fast, efficient, and perfect for most modern development workflows. We've optimized our container infrastructure to handle nearly every type of application you might need to run.

However, we also provide **VMs** when you need them, particularly for Docker-based workloads where the additional isolation is essential. Docker containers are a special case - in Zerops, they actually need to run inside VMs for proper security and isolation. While it's technically possible to run Docker in containers using privileged mode, this creates security vulnerabilities.

### When to Use What

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  <div className="flex-1">
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    Go with Containers when:
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        <span>Building modern web applications</span>
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        <span>Working with microservices</span>
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      <li className="flex items-center gap-0.5">
        <div className="w-0.5 min-w-0.5 shrink-0 aspect-square rounded-full bg-gray-400 flex items-center justify-center scale-75" />
        <span>Need quick deployment and vertical scaling</span>
      </li>
      <li className="flex items-center gap-0.5">
        <div className="w-0.5 min-w-0.5 shrink-0 aspect-square rounded-full bg-gray-400 flex items-center justify-center scale-75" />
        <span>Want efficient resource usage</span>
      </li>
  </ul>
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  <h4 className="flex items-center gap-1 mb-0">
    Consider VMs when:
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  <ul className="list-none p-0 m-0 flex flex-col gap-0.5">
      <li className="flex items-center gap-0.5">
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        <span>Running legacy applications</span>
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      <li className="flex items-center gap-0.5">
        <div className="w-0.5 min-w-0.5 shrink-0 aspect-square rounded-full bg-gray-400 flex items-center justify-center scale-75" />
        <span>Need complete OS isolation</span>
      </li>
      <li className="flex items-center gap-0.5">
        <div className="w-0.5 min-w-0.5 shrink-0 aspect-square rounded-full bg-gray-400 flex items-center justify-center scale-75" />
        <span>Require specific hardware access</span>
      </li>
      <li className="flex items-center gap-0.5">
        <div className="w-0.5 min-w-0.5 shrink-0 aspect-square rounded-full bg-gray-400 flex items-center justify-center scale-75" />
        <span>Need to run Docker containers</span>
      </li>
  </ul>
  </div>
</div>

### Resource Allocation

Both containers and VMs in Zerops can have guaranteed resources:
- Specific CPU cores
- Dedicated memory
- Controlled disk space

The difference isn't in resource guarantee capabilities, but rather in how these resources are managed and isolated.

## The Bottom Line

For most modern development work, containers are the way to go. They're faster, more efficient, and easier to work with. VMs still have their place, but unless you have a specific reason to use them, containers will usually make your life easier.

*Remember: The goal is to spend less time managing infrastructure and more time building great applications. Choose the tool that lets you do that most effectively.*

:::tip Pro Tip
Not sure which to choose? Start with containers. You can always switch to VMs if you discover you need them for specific use cases.
:::