Tuesday, December 1, 1998

Managing clusters and intra-cluster traffic

HARD-CORE ADMIN

By Sergey Kagolovsky

Notes server clusters are a highly reliable method for providing continuous service to Notes clients. However, the reverse side of this solution is a higher load on the local network. This higher load is caused by an increase in network traffic in proportion to the number of servers in a cluster -- as the result of the data being transmitted and written. A solution to this problem can be the division of network and intra-cluster traffic into different network segments.

A sample segmented network

One example of this approach is to create a simple cluster consisting of two servers running Windows NT 4.0 SP 3. In our example, these servers are identified as SERVER1/COMPANY/RU and SERVER2/COMPANY/RU. The idea behind our solution is to create an additional network adapter in each server and bypass intra-cluster traffic in the created segment. The sequence of actions for tuning the system and the Notes-server is discussed below.

Adapter installation and network configuration

Install additional network adapters in servers and connect them together using MDIX UTP-cable. We think that today the optimal adapter to choose according to the criteria of output vs. price is a PCI adapter with 100 Mb/sec and duplex-support. Install appropriate drivers for Windows NT. Special attention has to be paid to the network configuration in Windows NT.

An optimal protocol for intra-cluster replication is TCP/IP, which is the Lotus-certified protocol for clusters. Therefore, even if this protocol is not used on the server, we strongly recommend that you add it into the Protocol section of the network control panel, as shown in Figure A.

FIGURE A

TCP/IP is almost always a protocol win. (click for larger image)

In standard TCP/IP there is a class of reserved IP addresses that can be used for internal purposes without limitation. These are the IP prefix numbers beginning 192.168. Each new installed adapter has to be configured this way, so that all adapters will be at the same IP-subnetwork. This will avoid the need for routing. For example, you'd set up Server 1/Company/RU and Server 2/Company/RU to be exactly the same prefix, but different final IP addresses. So you might set up Server 1 to be at 192.168.3.3 and Server 2 at 192.168.3.9, as shown in Figure B.

FIGURE B

Here's the IP address for Server 2/Company/RU. (click for larger image)

Lastly, you'll want to set the network bindings to prohibit connection of all protocols except TCP/IP to the new installed adapter, as shown in Figure C.

FIGURE C

Prohibit all protocols except our favorite TCP/IP. (click for larger image)