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Server Mirroring with Novell's StandbyServer for NetWare

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01 Oct 1998

This NetNote describes StandbyServer for NetWare, one of Novell's high availability products. StandbyServer is a hardware-independent, high-availability solution that connects one or more secondary servers directly to the main server. Data is mirrored between the servers to create a fully redundant system that protects users against server failures. In case of a primary server failure, the standby machine can automatically take over server operations with no interruption to user productivity.

Since server downtime can be attributed to either hardware or, more commonly, software faults, any high-availability paradigm must be able to handle both types of failures. With StandbyServer, a second machine becomes the active server and is back online in a matter of minutesall automatically. StandbyServer provides a high degree of system flexibility, ease of use, and open configuration. No proprietary disk systems, monitoring devices, or special operating system software is required.

This solution also provides flexibility in server maintenance and updates. The primary server can be easily brought down, at which point StandbyServer switches all server functions to the standby machine. SNMP-compliant applications can send messages to administrators and users indicating the current status of StandbyServer and its configured mirror sets.

How StandbyServer Works

StandbyServer uses a second local server as a standby machine in case the primary server fails. Data from the primary server is mirrored to the standby machine, as well as other local or remote machines if desired, using standard network connections. Instead of copying files from one machine to the other, StandbyServer uses real-time NetWare disk mirroring to keep exact copies of all system data on both the primary and standby machines for true data protection.

Dedicated Link and Failover

StandbyServer uses standard IPX or IP connections to transfer data. A dedicated link is not required, but is recommended to eliminate additional network traffic. Any Novell-certified IPX or IP network card and driver combination can be used for the dedicated link. Data can be routed, bridged, or use a shared, high-speed backbone.

The connection status of the StandbyServer link and the network link between the machines is constantly monitored to ensure that the primary server is operating. These multiple checks avoid inadvertent failovers to the designated standby machine caused by a client network or communications problem. If the primary server has failed, the designated standby machine automatically assumes the role of the primary server using the same server name, login scripts, bindery or NDS and IPX or IP addresses as the failed server.

When using 32-bit client software from Novell or Microsoft, users experience only a momentary pause while the failover takes place, and their connection to the server is retained. With older client software, the users simply log back into the server using the same name and password as they do on the failed server.

Network users and administrators can be notified of failures through SNMP messaging services. This means that scheduled or unplanned server maintenance and server updates can take place during normal business hours.

Hardware and Software Compatibility

StandbyServer is compatible with:

  • All NetWare-compliant server configurations

  • All NetWare-certified ODI compliant network adapters

  • IPX and IP network protocols

  • All NetWare/intraNetWare-certified NetWare Loadable Modules

In addition to the standard one-to-one configuration, Standby-Server also comes in a many-to-one version that allows multiple primary servers to be protected by a single standby machine.

To implement StandbyServer, you will need two or more machines capable of running NetWare 3.12 or 4.11. The hardware need not be identical, but each machine must have a Novell-certified network adapter. Additional adapters are required for a dedicated link.

Disk devices in the standby machine must be supported by NetWare drivers. They do not need to be identical to the disk devices in the primary server. NetWare mirroring requirements also apply when using StandbyServer. For instance, hard drives in the machines may be different sizes, but partition sizes must be identical. Familiarity with NetWare mirroring increases your ability to optimize the features of StandbyServer.

The StandbyServer family of products provides an effective solution for automatic recovery. StandbyServer takes advantage of the economies and performance of industry-standard hardware to extend the configuration capabilities and flexibility of implementing automatic server failover to a standby machine.

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* Originally published in Novell AppNotes


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