Low-cost dual-computer fault tolerant scheme for UNIX platform

There are many ways to improve system availability, but each has its pros and cons, so designers often have to choose a different solution based on the actual reliability and availability requirements of the user. This also depends on the requirements of the system: hardware fault-tolerant solutions tend to run faster but have large investments, and software fault-tolerant solutions may consume overhead, but are more flexible than hardware solutions, especially after the system has been built and investment is small. The fault-tolerant system introduced in this paper is to realize the system's usability by means of software, without the use of array cabinets or other special hardware, in order to improve the availability of the system, by using the technology of the wave-Western server reliability platform and the special-purpose micro.

Equipment selection

In this scenario, we use the wave of the English server-Netcom NL300, this is because the server has the following distinctive features, especially in the reliability, performance, scalability are outstanding performance:

With the latest Intel Pentiumⅲxeon processor, excellent performance, high reliability, strong scalability. At the same time, the industry's advanced system architecture, including 133MHz SDRAM, 64-bit/66mhz PCI, and the latest FSB 133MHz of the Intel Pentiumⅲxeon processor, provides a two-way server to provide the super performance.

In addition to ultra strong performance, in order to protect the user's investment, so that the server can continue to improve performance as the user's business grows, netcom NL300 reserves sufficient internal expansion capability: The system provides 16 storage slots, including 9 hot-swappable hard disk slots to meet the growing storage requirements of the users. ; The system provides 6 PCI slots and one ISA slot, and supports the latest 64-bit PCI technology to install High-performance expansion cards to meet your ever-increasing performance requirements, plus memory can be extended to 4GB and support two-way processors. Maximize the protection of investment.

In addition, in order to ensure the stable operation of the user's key business, Netcom NL300 provides extremely high availability, including ECC memory, hot-swappable hard disk, hot-swappable power supply and fault prediction technology. Features that are owned by a previous high-end computer.

System Platform

Tide netcom NL300 Server Two (can be different configuration, configure dual network card);

SCO UNIX Operating system two sets;

A set of database systems;

Savwareha software set;

RS232 Serial line, CAT5 type Direct (NO HUB) cable each one.

We can see clearly from the above figure that two servers are equipped with dual network adapters, each of which is connected to the public network through one of the network cards, which provides services to other customers on the net. And another pair of NIC for the interconnection between them, this channel is in the two servers for a large number of data transfer between the dedicated channel, which is responsible for the transfer of data between the two hosts, and the serial line between the two machines pass heartbeat signal, used to detect the status of the server to determine whether the business and host address of the takeover.

System Work Process

1) Automatic detection (auto-detect) phase: