NetScaler VPX Capacity Planning/Sizing

Q: Given that server CPU power will vary, how can we estimate maximum performance of a NetScaler VPX instance?

A: Using a faster CPU could result in higher performance (up to the maximum allowed by the license), while using a slower CPU can certainly limit the performance.

Q: Are NetScaler VPX bandwidth/throughput limits for inbound only traffic, or both inbound and outbound traffic?

A: NetScaler VPX bandwidth limits are enforced for traffic inbound to the NetScaler only, regardless of whether this is request traffic or response traffic. This indicates that a NetScaler VPX-1000 (for example) can process both 1 Gbps of inbound traffic and 1 Gbps of outbound traffic simultaneously. Note that inbound and outbound traffic are not the same as request and response traffic. To NetScaler, both traffic coming from endpoints (request traffic) and traffic coming from origin servers (response traffic) is "inbound" (that is, coming into the NetScaler).

Q: Can multiple instances of NetScaler VPX be run on the same server?

A: Yes. However, ensure that the physical server has enough CPU and I/O capacity to support the total workload running on the host, or NetScaler VPX performance could be impacted.

Q: If more than one instance of NetScaler VPX is running on a physical server, what is the minimum hardware requirement per NetScaler VPX instance?

A: Each NetScaler VPX instance should be allocated 2GB of physical RAM, 20 GB of hard disk space, and 2 vCPUs.

Q: Can I host NetScaler VPX and other applications on the same server?

A: Yes. For example, NetScaler VPX, XenApp Web Interface and XenApp XML Broker could all be virtualized and can run on the same server. For best performance, ensure that the physical host has enough CPU and I/O capacity to support all the running workloads.

Q: Will adding CPU cores to a single NetScaler VPX instance increase the performance of that instance?

A: Depending on the license, a NetScaler VPX instance can use up to 4 vCPU today. Adding additional CPU to a NetScaler VPX instance that can use more CPUs will increase the performance.

Q: Even though NetScaler VPX is idle, it looks like it is consuming more than 90% of CPU. Why is this?

A: This is normal behavior and NetScaler appliances exhibit the same behavior. To see the true extent of NetScaler VPX CPU utilization, use the stat cpu command in the NetScaler CLI, or view NetScaler VPX CPU utilization from the NetScaler GUI. The NetScaler packet processing engine is always "looking for work", even when there is no work to be done. Therefore, it will do everything it can to take control of the CPU and not release it. On a server installed with NetScaler VPX and nothing else, this results in it looking like (from the hypervisor perspective) that NetScaler VPX is consuming the entire CPU. Looking at the CPU utilization from "inside NetScaler" (by using the CLI or the GUI) provides a picture of NetScaler VPX CPU capacity being used.