Virtual Scanner Appliance Sizing
This section provides guidance on sizing the Virtual Scanner Appliance to ensure optimal performance and stability based on your scanning needs.
Default Configuration
The Qualys Virtual Scanner Appliance is provisioned with the following default configuration:
| Resource | Default Value |
|---|---|
| vCPU | 4 |
| Memory (RAM) | 8 GB |
| Disk Space | 56 GB |
In version 3.10, restrictions are lifted, allowing you to configure more than 16 vCPUs and 16 GB of RAM.
Recommended vCPU: RAM Ratio
The default vCPU-to-RAM ratio is sufficient for some cases. You can increase the number of vCPUs and memory resources to enhance your scanning capacity. However, it is essential to maintain a vCPU-to-memory ratio of either 1:3 or 1:2, depending on your platform's flexibility for scaling adjustments.
Qualys recommends a maximum of 64 GB of RAM, proportionally matched with the vCPU at a 1:3 or 1:2 ratio. For example, if you set the scanner to use 64 GB of RAM, you should configure it to have either 20 or 32 vCPUs.
However, if your virtual scanner needs to handle a large number of scan targets, increasing the RAM size boosts scanning capacity (though not speed). It helps prevent the scanner from becoming overloaded.
The following table shows the outcomes for the recommended and not recommended vCPU: RAM ratio:
| vCPU: RAM Ratio | Recommendation | Outcome |
|---|---|---|
| 1:3 | Optimal | Ideal balance for performance and stability |
| 1:2 | Acceptable | Works based on platform flexibility |
| >1:3 | Suboptimal | May cause vCPU bottlenecks and underutilized memory |
| <1:2 | Not recommended | Risk of memory overcommitment; may cause scan failures |
Work directly with your Technical Account Manager or Qualys Support for help with scanner capacity and sizing calculations based on your scanning needs.
Increase Virtual Disk Size
Increasing the disk size is only needed if you frequently encounter low disk space issues during scans. Otherwise, you do not need to increase the disk size even if you increase the vCPU and memory.
- Disk size should only be increased when debug mode is enabled, as instructed by Qualys Support.
- You can only increase the disk size; reducing the size is not supported.
To increase the virtual disk size, perform the following steps:
- Stop the scanner instance.
- Find the Hard Disk/Storage option in your scanner VM instance settings and increase the disk size.
- Save your settings and start up your scanner.
Your scanner instance should generate the new disk size. It also automatically resizes all partitions and file systems.
Change vCPU and RAM Size
You can increase or decrease vCPU and RAM.
The maximum supported size for a scanner instance is 64 GB RAM with a vCPU: RAM ratio of 1:3 or 1:2. Allocating more memory than this will be wasted.
As mentioned earlier, the number of vCPUs must be proportional to the allocated RAM and disk space. Use a ratio of 1:2 or 1:3 for vCPU: RAM. For example, 4 vCPUs with 12GB RAM or 8 vCPUs with 16 GB of RAM.
To change the vCPU/RAM allocated for a scanner instance, perform the following steps:
- Stop the scanner instance.
- Find the vCPU/RAM options in your scanner VM instance settings and choose the desired size.
- Save your settings and start up your scanner.