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Speed up cluster resource failover by changing the unload script

(Last modified: 05May2004)

This document (10086057) is provided subject to the disclaimer at the end of this document.

goal

Speed up cluster resource failover by changing the unload script

fact

Novell Cluster Services 1.01

Novell Cluster Services 1.6

symptom

Cluster resource failover / migration is slow or hangs

cause

Changes were made to NUDP to allow for a more gracefull client disconnect. The new way waits until all NCP connections have terminated which can vary in time depending on what the connections are doing (file copy, etc.). Using the ODEL parameter forces the virtual server to be deleted after a fixed amount of time.

The difference between NUDP DEL and NUDP ODEL is that NUDP DEL will wait to be notified by each connection that it has fully closed, where as, NUDP ODEL will simply notify the connections that they need to close and then proceed with the rest of the volume migration. The NUDP DEL command is a little bit cleaner with respect to client connections allowing the reconnect to happen faster and more efficient.

The sequence of events during a volume migration should be that the clients are notified that the connection is lost and they simply do a reconnect. File handles are not reconnected since they do not exist on the new server. Any pending file operations would error out and the application should handle that. In the case of a simple file copy, the user should get an error message that the file copy failed so they can restart it. 

ODEL says finish no matter what the state of the TCP connection is. There will be no hang because ODEL doesn't wait for the TCP connection to clean up properly - so when ODEL completes,  the TCP connection will probably still be in the closeWait state as shown in tcpcon. But ODEL also deletes the secondary IP address, so if the client hadn't finished its handshake it will never be able to. This usually results in the client eventually timing out and resetting the connection sometime later.

fix

Change NUDP DEL to NUDP ODEL in the resource unload script

disclaimer

The Origin of this information may be internal or external to Novell. Novell makes all reasonable efforts to verify this information. However, the information provided in this document is for your information only. Novell makes no explicit or implied claims to the validity of this information.
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  • Document ID:
  • 10086057
  • Solution ID: NOVL91732
  • Creation Date: 11Aug2003
  • Modified Date: 05May2004
    • NovellNetWare

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