Synology VMM as File Server: Yes, But Know This

Yes, you can use Synology Virtual Machine Manager (VMM) as a file server, but it is almost always the wrong tool for the job. VMM lets you run a full virtual machine (VM) on your NAS, and that VM can host a file server (Windows, Linux, or a dedicated NAS OS), but your Synology’s native file services are faster, simpler, and more efficient. This article explains what VMM actually does, how it compares to using the built-in file server, and when (if ever) running a VM for file storage makes sense.

What Synology Virtual Machine Manager Actually Does

Synology Virtual Machine Manager is a hypervisor built into DiskStation Manager (DSM) that runs on certain Synology NAS models. It lets you create and run virtual machines—complete operating systems with their own virtual CPU, RAM, and disk—on the same hardware that runs your NAS. You can install Windows, Linux, or even a lightweight NAS OS like OpenMediaVault or TrueNAS Core inside a VM. Each VM gets its own virtual disk, which is stored as a file on your Synology’s storage pool.

VMM is designed for running lightweight workloads: a small Linux server, a Windows VM for an occasional application, or a test environment. It is not designed to replace the NAS’s own file services. Synology’s native file server (SMB, NFS, AFP, WebDAV) runs directly on the host OS and has direct access to the storage pool, bypassing the hypervisor and the virtual disk layer entirely.

How a VM File Server Works (and Why It’s Slower)

When you run a file server inside a VM, the data path looks like this:

• Client sends a file request over the network to the VM’s IP address.
• The VM’s operating system processes the request and reads/writes to its virtual disk.
• The virtual disk is actually a large file (or a set of files) stored on the Synology’s underlying storage pool.
• The hypervisor translates those reads/writes into real disk I/O on the NAS’s physical drives.

That extra layer adds overhead. The VM’s operating system also consumes CPU and RAM that could otherwise be used for caching, file transfers, or other NAS services. In practice, you can expect a VM-based file server to deliver noticeably lower throughput and higher latency than the native SMB service, especially with many simultaneous clients.

For example, a Synology DS920+ with native SMB can easily saturate a 1GbE link (around 110-120 MB/s). The same NAS running a Windows VM with a virtual disk will often top out at 60-80 MB/s, and it will use a significant chunk of the available RAM just for the VM’s operating system.

Why You’d Even Consider a VM File Server

There are a few legitimate reasons someone might want to run a file server in a VM on their Synology:

• Software compatibility: You need a file server feature that DSM doesn’t provide natively. For example, you want to run a specific NFS implementation, a Windows Server with Active Directory, or a specialized file-sharing application that only runs on a particular OS.
• Isolation: You want to keep a file server completely separate from the NAS’s main operating system, perhaps for security or testing purposes. A VM provides a sandboxed environment.
• Learning: You want to practice setting up a file server on a real OS (like Windows Server or Linux) without buying separate hardware.
• Migration: You’re moving from an old server that runs a specific OS and you want to keep the same environment, rather than migrating to DSM’s native file services.

These are edge cases. For 95% of home users and small businesses, the native file server is the right choice.

Native File Server vs. VM: A Real Comparison

Let’s put the two side by side:

• Performance: Native SMB/NFS is significantly faster because it has direct access to the storage pool. VMM adds a virtual disk layer that slows everything down.
• Resource usage: A VM needs a fixed allocation of RAM and CPU, which is then unavailable for other NAS tasks. Native file services use almost no overhead.
• Management: Native file services are managed through DSM’s web interface—simple, integrated, and reliable. VMs require you to manage a full operating system, apply updates, and troubleshoot software issues.
• Reliability: Native file services are tightly integrated with the NAS’s kernel and storage stack. A VM is another layer of software that can crash, hang, or need a reboot.
• Power consumption: A VM keeps the CPU busy even when idle, increasing power draw and heat. Native services are idle when not in use.
• Backup: Native shared folders are easy to back up with Hyper Backup. VM disks are large files that you can back up too, but they’re less efficient.

In short, the native file server wins on every practical metric except for the specific need to run a non-DSM operating system.

When a VM File Server Makes Sense

There are a few scenarios where the trade-off is worth it:

• Running Windows Server for Active Directory: If you need AD for your network, you can’t get that from DSM. A Windows VM is the only way.
• Running a specialized NAS OS like TrueNAS: TrueNAS offers features like ZFS snapshots and advanced replication that DSM doesn’t have. Some users run TrueNAS in a VM on a Synology to get those features.
• Testing and development: If you’re a developer or IT professional, VMM is a great way to spin up a test file server without dedicated hardware.

In these cases, you’re not using VMM as a replacement for the native file server—you’re using it to run an entirely different operating system that happens to provide file services.

Common Problems and Misconceptions

One common misconception is that a VM file server will be more secure or more reliable because it’s

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