Evidian > Products > High Availability Software - Zero Extra Hardware > Microsoft NLB in VMware: alternative to multicast and unicast with the SafeKit software
As explained in the knowledge base of VMware on network load balancing (NLB) multicast mode configuration, you 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.
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, Microsoft NLB is not working properly in Unicast Mode with VMware.
The SafeKit virtual IP address configuration does not require any special network configuration and the network load balancing can run in any environment. An important feature when the solution must be deployed in an unknown infrastructure: unknown switches or routers, physical servers or virtual servers.
This platform agnostic solution is ideal for a partner with a critical application and who wants to provide a high availability option easy to deploy to many customers.
This clustering solution is also recognized as the simplest to implement by our partners.
On the previous figure, the application is running on the 3 servers (3 is an example, it can be 2 or more). Users are connected to a virtual IP address.
The virtual IP address is configured locally on each server in the farm cluster.
The input traffic to the virtual IP address is received by all the servers and split among them by a network filter inside each server's kernel.
SafeKit detects hardware and software failures, reconfigures network filters in the event of a failure, and offers configurable application checkers and recovery scripts.
The network load balancing algorithm inside the network filter is based on the identity of the client packets (client IP address, client TCP port). Depending on the identity of the client packet input, only one filter in a server accepts the packet; the other filters in other servers reject it.
Once a packet is accepted by the filter on a server, only the CPU and memory of this server are used by the application that responds to the request of the client. The output messages are sent directly from the application server to the client.
If a server fails, the SafeKit membership protocol reconfigures the filters in the network load balancing cluster to re-balance the traffic on the remaining available servers.
With a stateful application, there is session affinity. The same client must be connected to the same server on multiple TCP sessions to retrieve its context on the server. In this case, the SafeKit load balancing rule is configured on the client IP address. Thus, the same client is always connected to the same server on multiple TCP sessions. And different clients are distributed across different servers in the farm.
With a stateless application, there is no session affinity. The same client can be connected to different servers in the farm on multiple TCP sessions. There is no context stored locally on a server from one session to another. In this case, the SafeKit load balancing rule is configured on the TCP client session identity. This configuration is the one which is the best for distributing sessions between servers, but it requires a TCP service without session affinity.
Evidian SafeKit mirror cluster with real-time file replication and failover |
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Fully automated failback procedure > |
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Replication of any type of data > |
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File replication vs disk replication > |
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File replication vs shared disk > |
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Remote sites and virtual IP address > |
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Uniform high availability solution > |
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Evidian SafeKit farm cluster with load balancing and failover |
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No load balancer or dedicated proxy servers or special multicast Ethernet address > |
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Remote sites and virtual IP address > |
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Uniform high availability solution > |
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Application High Availability vs Full Virtual Machine High Availability > |
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Byte-level file replication vs block-level disk replication > |
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Virtual IP address |
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Network load balancing and failover |
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Windows farm |
Linux farm |
Generic farm > | Generic farm > |
Microsoft IIS > | - |
NGINX > | NGINX > |
Apache > | Apache > |
Amazon AWS farm > | Amazon AWS farm > |
Microsoft Azure farm > | Microsoft Azure farm > |
Google GCP farm > | Google GCP farm > |
Other cloud > | Other cloud > |
Several modules can be deployed on the same cluster. Thus, advanced clustering architectures can be implemented: