# The VM Storage Identity Crisis: Why Your NVMe SSD Appears as HDD

You’ve invested in a blazing-fast NVMe SSD for your host, you're running **XCP-ng/Xen**, and your Virtual Machines are humming along. But then you peek into Task Manager in **Windows Server 2022**, and your drive is labeled **"HDD."** Meanwhile, your **Server 2019** VM shows no label at all.

This isn't a bug, and your performance isn't being throttled. It’s a side effect of how different OS versions interpret the **Xen Paravirtual (PV)** storage path.

---

## 1\. The Core Problem: Virtualization vs. Reality

When you create a VM, the hypervisor presents a virtual disk via a virtualized controller. For XCP-ng, this is the **Xen PV SCSI Host Adapter**. In Windows, this appears as a **"XENSRC PVDISK SCSI Disk Device."**

Because the connection type is **SCSI**, modern Windows versions have to make a choice:

* **Windows Server 2019:** Often leaves the "Media Type" field **blank**. It doesn't want to guess the hardware type if it isn't explicitly told.
    
* **Windows Server 2022:** Microsoft updated the UI to be more specific. If the OS sees a SCSI bus and hasn't received a "Non-Rotational" flag from the host, it defaults to the **HDD** label because SCSI has historically been mechanical storage.
    

---

## 2\. Windows Verification: Checking the "Truth"

Don't trust the Task Manager icon. Use these commands to see exactly what is happening under the hood.

### The Driver Check

First, ensure your Guest Tools are healthy. In **Device Manager**, you should see **XENSRC PVDISK**. This confirms you are using the high-performance PV driver rather than a generic emulated one.

### The PowerShell Diagnostic

The "Media Type" listed here is what Windows uses to decide whether to **Defrag** (Bad for SSD) or **TRIM** (Good for SSD).

PowerShell

```plaintext
# Check how Windows identifies the hardware
Get-PhysicalDisk | Select-Object FriendlyName, MediaType, BusType, OperationalStatus
```

* **FriendlyName:** `XENSRC PVDISK` confirms your Guest Tools are active.
    
* **MediaType:** `Unspecified` is the culprit. When Windows sees this, Server 2022/2019 defaults to "HDD."
    
* **BusType:** `SCSI` is the paravirtualized path used for high performance.
    

---

## 3\. Linux Verification: Rotational vs. SSD

Linux is much more transparent. It uses a binary "Rotational" (ROTA) flag: **1** for spinning, **0** for solid state.

### The `lsblk` Command

Run the following to check your drive status (usually `xvda` or `xvdb` in Xen):

Bash

```plaintext
lsblk -d -o NAME,ROTA,TYPE,SIZE
```

* **ROTA = 0**: The kernel correctly identifies it as an SSD.
    
* **ROTA = 1**: The kernel thinks it's a spinning disk.
    

### Verify TRIM (Discard) Support

Even if the label is wrong, check if the OS can "TRIM" the drive:

Bash

```plaintext
lsblk --discard
```

If **DISC-GRAN** shows a value (like 4K), your VM is successfully communicating with the underlying NVMe.

---

## 4\. The Real Fix: Host-Level Flagging

Since Windows and Linux can't always change their "hardware" identity from the inside when the media type is "Unspecified," you must tell the XCP-ng host to "advertise" the SSD status.

**Run these commands on your XCP-ng Host CLI (Not inside the VM):**

1. **Find your VM's UUID:**
    
    `xe vm-list name-label="Your_VM_Name"`
    
2. **Find the VBD (Virtual Block Device) UUID for that VM:**
    
    `xe vbd-list vm-uuid=<VM_UUID>`
    
3. **Set the SSD flag on the VBD:**
    
    `xe vbd-param-set uuid=<VBD_UUID> device-config:type=ssd`
    
4. **Restart the VM.**
    

---

## Final Comparison Summary

| **Feature** | **Windows Server 2019** | **Windows Server 2022** | **Linux (Ubuntu/Debian)** |
| --- | --- | --- | --- |
| **Default UI Label** | **(Blank/None)** | **HDD** | **ROTA: 0** (Usually Correct) |
| **Driver Name** | XENSRC PVDISK | XENSRC PVDISK | xvda / sda |
| **Bus Type** | SCSI | SCSI | SCSI/PV |
| **Performance** | Native NVMe Speed | Native NVMe Speed | Native NVMe Speed |

**The Bottom Line:** Your "HDD" is actually a high-speed NVMe. The label in Windows 2022 is a visual placeholder for the SCSI bus. As long as your PowerShell shows **OperationalStatus: OK**, you are running at full speed!