Load balancing Kofax eCopy ShareScan

How to load balance Kofax eCopy ShareScan

The following diagram illustrates how the load balancer is deployed with multiple eCopy ShareScan servers.

Note: The load balancer can be deployed as a single unit, although Loadbalancer.org recommends a clustered pair for resilience & high availability.
Please refer to section 2 in the Deployment Guide for more details on configuring a clustered pair.

The load balancer can be deployed in 4 fundamental ways: Layer 4 DR mode, Layer 4 NAT mode, Layer 4 SNAT mode and Layer 7 SNAT mode. However, for eCopy ShareScan, Layer 7 SNAT mode cannot be used and where possible we recommend that Layer 4 Direct Routing (DR) mode should be used. This mode offers the best possible performance since replies go directly from the eCopy ShareScan servers to the client, not via the load balancer. It’s also relatively simple to implement. Ultimately, the final choice does depend on your specific requirements and infrastructure.

Layer 4 DR Mode

One-arm direct routing (DR) mode is a very high performance solution that requires little change to your existing infrastructure.

• DR mode works by changing the destination MAC address of the incoming packet to match the selected eCopy ShareScan server on the fly which is very fast
• When the packet reaches the eCopy ShareScan server it expects the server to own the Virtual Services IP address (VIP). This means that you need to ensure that the eCopy ShareScan server (and the load balanced application) respond to both the eCopy ShareScan servers own IP address and the VIP
• The eCopy ShareScan server should not respond to ARP requests for the VIP. Only the load balancer should do this. Configuring the eCopy ShareScan servers in this way is referred to as Solving the ARP Problem. please refer to chapter 6 in the Administration Manual for more information
• On average, DR mode is 8 times quicker than NAT for HTTP, 50 times quicker for Terminal Services and much, much faster for streaming media or FTP
• The load balancer must have an Interface in the same subnet as the eCopy ShareScan servers to ensure layer 2 connectivity required for DR mode to work
• The VIP can be brought up on the same subnet as the eCopy ShareScan servers, or on a different subnet provided that the load balancer has an interface in that subnet
• Port translation is not possible in DR mode i.e. having a different RIP port than the VIP port
• DR mode is transparent, i.e. the eCopy ShareScan server will see the source IP address of the client

For details on Layer 4 NAT mode please refer to the full Deployment Guide.