Microsoft NLB in VMware: alternative to multicast and unicast with the SafeKit software

Microsoft NLB in VMware: alternative to multicast and unicast with the SafeKit software

Microsoft NLB multicast mode

As explained in the knowledge base of VMware, in the case of Microsoft NLB multicast modeyou need to manually configure static ARP resolution at the switch or router for each port that connects to the cluster.  Deployment of the Microsoft NLB multicast mode in an unknown network environment can prove to be a complex and strenuous task.

Microsoft NLB unicast mode

With Microsoft NLB unicast mode, you must configure the ESXi/ESX host to not send RARP packets when any of its virtual machines is powered on. That's why, VMware recommends configuring the cluster to use NLB multicast mode with the previously mentioned problems.

Alternative with the virtual IP address of Evidian SafeKit

With the SafeKit software, network load balancing is implemented by filtering packets in the network stacks as with Microsoft NLB. The virtual IP address is set as an alias IP address on the NIC card of each physical or virtual machine. A single network is sufficient to implement network load balancing, without the  prerequisite of two network cards and two IP networks as required by Microsoft NLB unicast mode.

The virtual IP address configuration does not require any special network configuration and the network load balancing can run in any environment (thanks to the vmac_directed technology). An important feature when the solution must be deployed in an unknown infrastructure: unknown switches or routers, physical servers or virtual servers.

Note that the solution is available on Windows and Linux (even on Windows editions for PCs).

Key differentiators of load balancing and failover with the Evidian SafeKit farm cluster

Evidian SafeKit farm cluster with load balancing and failover

No load balancer or dedicated proxy servers or special multicast Ethernet address No load balancer or dedicated proxy servers

Like   The solution does not require load balancers or dedicated proxy servers above the farm for imlementing load balancing. SafeKit is installed directly on the application servers in the farm. The load balancing is based on a standard virtual IP address/Ethernet MAC address and is working with physical servers or virtual machines on Windows and Linux without special network configuration

Dislike  This is not the case with network load balancers

Dislike  This is not the case with dedicated proxies on Linux

Dislike  This is not the case with a specific multicast Ethernet address on Windows

All clustering features All clustering features

Like  The solution includes all clustering features: virtual IP address, load balancing on client IP address or on sessions, server failure monitoring, network failure monitoring, software failure monitoring, automatic application restart with a quick revovery time and a replication option with a mirror module. A clustering configuration is simply made by means of a high availability application module. There is no domain controller or active directory to configure on Windows. The solution works on Windows and Linux

Dislike  This is not the case with other load balancing solutions. They are able to make load balancing but they do not include a full clustering solution with restart scripts and automatic application restart in case of failure. They do not offer a replication option

Remote sites Remote sites

Like   If servers are connected to the same IP network through an extended LAN between remote sites, the virtual IP address of SafeKit is working with load balancing at level 2

Like   If servers are connected to different IP networks between remote sites, the virtual IP address can be configured at the level of a load balancer. SafeKit offers a health check: the load balancer is configured with a URL managed by SafeKit which returns OK on the UP servers and NOT FOUND else. This solution is implemented for SafeKit in the Cloud but it can be also implemented with a load balancer on premise. Thus you can implement load balancing but also all the clustering features of SafeKit including an easy administration of the cluster through the SafeKit web console

Dislike   Load balancers do not implement all the clustering features of SafeKit

Uniform high availability solution Uniform high availability solution

Like  SafeKit imlements a farm cluster with load balancing and failover. But it implements also a mirror cluster with replication and failover. Thus a N-tiers architecture can me made highly available and load balanced with the same solution on Windows and Linux (same installation, configuration, administration with the SafeKit console or with the command line interface). This is unique on the market

Dislike  This is not the case with an architecture mixing different technologies for load balancing, replication and failover

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