For many years server load-balancing appliances have been a luxury only enterprises could afford but we’re now seeing a number of solutions targeting smaller business on strict budgets. The temptingly priced Kemp LoadMaster 1500 impressed us enough to earn it a Recommended award and in this exclusive review we see what newcomer ClusterScale has to offer.
The Pegasys appliance represents the entry point of the ClusterScale appliance family and has at its foundation a good quality Dell PowerEdge R200 rack server. Standard features are web server load balancing, Layer 4/7 content switching and the ability to handle up to seven million concurrent L4 sessions.
The Pegasys doesn’t have hardware-assisted SSL termination so can handle only 150 TPS – the ASIC in the similarly priced LoadMaster 2500 can manage 1,000 TPS. However, the Pegasys doesn’t limit the number of supported physical and virtual servers making the price of £3,995 for a single appliance look good value.
On review we have the more popular HA (High Availability) solution which comprises a pair of appliances linked via a serial cable for heartbeat operations.
ClusterScale’s muddled and badly written documentation doesn’t help installation. Note also that IE6 isn’t supported for appliance administration. Firefox worked fine but we also had some problems using IE7; these were mainly style sheet issues that should be easily remedied.
The web interface provides easy access to each function but it’s minimalist to say the least, while non-Linux fans won’t like features such as the configuration-viewing section – this simply shows the various settings in command line format.
Although the Pegasys can use NAT between physical and virtual servers, it’s more focused towards direct routing. This provides superior performance and allows virtual and physical servers to be on the same subnet, but there is a downside: direct routing changes the MAC address of inbound packets to direct them to the appropriate physical server.
During farm setup you need to install a loopback network adapter on each server, otherwise they’ll drop the incoming packets as they have an incorrect IP address in them.
We started testing with direct routing but had problems with FTP client connection failures that we couldn’t resolve. NAT proved to be more successful and we ran a server farm providing web, mail and FTP services to our test clients, which were located on a different subnet.
During large file transfers we could see our clients being sent to servers using round robin weighting and when we pulled the plug on the master appliance the slave stepped in, promptly allowing the copies to continue unabated.
Weightings on each server in the farm determine their priority for receiving requests and you can set limits on the minimum and maximum connections. Layer 4 persistence is determined by source and destination IP addresses, while Layer 7 inspection allows you to use functions such as cookies to ensure clients are always sent to the same physical servers.
The Pegasys appliance is offering a good range of features and ClusterScale’s on-site warranty is a cut above the rest. It’s easy to see why the HA solution is popular as it’s very simple to configure and represents good value – but until ClusterScale smoothes off a lot of rough edges, the Kemp Technologies LoadMasters are a more sophisticated alternative.
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