ClusterScale Nemasys

Server load balancing can be an expensive option as although many solutions offer a high feature count these do come at an equally high price. ClusterScale aims to deliver a more cost-effective alternative as its ClusterLoad family of appliances delivers a solid range of load balancing capabilities but at a much more tempting price.

The family consists of two models and on review we have the Nemasys appliance, which targets mid-range businesses and enterprises. ClusterScale certainly gets our thumbs up for its hardware package as the appliance has at its foundation a quality Dell PowerEdge 1950 1U rack server, which came kitted out with a pair of the latest 2.33GHz E5410 quad-core Xeon processors. Coming in at £7,000 for a single appliance, the Nemasys looks good value but here we look at the more popular HA (high availability) package, which comprises identical master and slave appliances linked via a serial cable for heartbeat operations.

The Nemasys delivers web server load balancing and Layer 4/7 content switching and ClusterScale claims it can handle up to fourteen million concurrent L4 sessions. The appliance employs the server’s processors for SSL termination and it can handle up to 4,000 TPS. A feature that makes the Nemasys even better value is that ClusterScale doesn’t place any license restrictions on the number of physical and virtual servers.

The Nemasys adheres to the standard concepts for server load balancing as you create farms using multiple physical servers on the LAN and assign these to virtual servers facing the public side of your network. The appliance offers a number of deployment scenarios and supports both one-arm and two-arm modes with the latter enabling physical and virtual servers to be placed in different subnets. Along with NAT routing the Nemasys also supports DR (direct routing) and SNAT (source NAT) between physical and virtual servers.

DR provides a superior performance and enables virtual and physical servers to be on the same subnet but the drawback is a more complex configuration is required. DR changes the MAC address of inbound packets to direct them to the appropriate physical server but during farm setup you will need to install a loopback network adapter on each server otherwise they will drop the incoming packets as they have an incorrect IP address in them.

Note also that if you go for the DR mode you will have to make some configuration changes to get FTP services to work. The Nemasys provides a basic firewall and this will need a script change to ensure that all FTP packets are sent to the same initial physical server, which means DR mode only supports persistent connections for FTP.

ClusterScale was in our testing lab earlier this year when we looked at the lower-end Pegasys appliance in our sister title PC Pro Business (web ID:191520). Alas, it didn’t fair too well as we weren’t overly impressed with the muddled and badly written documentation, the lack of support for IE6 for appliance administration and the style sheet issues we encountered with IE7. We didn’t think much of the minimalist web management interface either, as it was poorly designed and confusing.

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