VZEN performance

Dear All,

We had just deployed a pair of vZEN with Medium license and hardware acceleration card, but the performance from user side is not met the expectation, ie the internet link is 100Mbps and user access via vZEN is only 50Mbps. As Zscaler analysis tool is not work in vZEN environment, therefore, we used speetdtest.net for testing the speed. The following I would like to clarify:

  1. With medium license, the maximum throughput should be support up to 100Mbps, and we deployed two vZEN appliances, can I expect the vZEN cluster is support totally 200Mbps?
  2. In vZEN cluster, the deployment guide is mentioned traffics are handled by Zscaler load balancer (LB), what is the technology behind the distributor traffics to two different vZEN instances? load balance or load share? by source or by destination?

Best Regards

Hi @Aldous, welcome to the Zscaler Community!

First thing, with regard to this:

… the internet link is 100Mbps and user access via vZEN is only 50Mbps …

Please open a support ticket, pulling the needed diagnostics is something our VZEN SME’s will glady help with, what you describe is unusual and is probably a configuration item. Naturally, if there’s any interesting finding(s)/solution, we should post back into this thread.

To your questions:

You could go active active and get such an aggregate throughout, however, you shouldn’t budget for this. ZEN’s follow an n+1 model at a minimum, as you only have 2 VZEN’s there can only be guaranteed throughout of 100mbps.

We use our own LB / HA technology, it primarily engineered around CARP principals. Under the hood each cluster has a shared VIP and cluster IP, you may have noted the need for promiscuous mode for the Vswitch network, this is needed to allow the inter-ZEN communications, as well return traffic to be sources from any instance in the cluster.

Given your setup with a 1+1 config, you are probably best to treat this like an active/passive HA config, but as described above, our LB technology is capable of much richer load balancing.


Customer find that using layer 2 instead of GRE helps to increase the performance to over 90% of the link speed. MTU is adjusted before the test.

Best Regards,

Jones Leung

SE Manager, Greater China

Zscaler, Inc

HK: +852 94636204

TW: +886 983 904 288