Exalytics T5-8: What is Recommended Setting for NFSv4 Delegation

Asset ID:	1-71-2144539.1
Update Date:	2016-07-29
Keywords:

Solution Type Technical Instruction Sure

Solution 2144539.1 : Exalytics T5-8: What is Recommended Setting for NFSv4 Delegation

Applies to:

Oracle Exalytics T5-8 - Version All Versions and later
Solaris Operating System - Version 11.1 and later
Information in this document applies to any platform.

Goal

When using an Exalytics T5-8 server with ZFS and NFSv4 mounted filesystems, frequent hangs are occurring while writing HFM actions to the HFM log file on ZFS. In the Exalytics ZFS, the NFSv4 delegation is currently enabled and hangs are occurring.

In the past, a similar issue was encountered with Exalogic server and ZFS. With Exalogic, the solution was to disable NFSv4 delegation, reference: <Document 1481713.1>, NFSv4 mount directories hang on Exalogic Machine (Doc ID 1481713.1)."

Is the Exalogic issue also a known issue with Exalytics T5-8 and ZFS? If yes, should delegation also be disabled for the Exalytics ZFS on the T5-8 server?

Solution

Our Development teams (Solaris, ZFS and Exalytics) have not found any instances where NFSv4 delegation settings caused hangs in ZFS.
NFSv4 delegation is designed to change the behavior if multiple client connections try to change the same file. This does not match the use case when hangs are encountered with HFM writing to the log file.

Accordingly, our Development teams recommend that you leave NFSv4 delegation set to the default (enabled). Additionally, Development does not recommend altering default settings without thoroughly analyzing the potential performance impact of the change on your specific environment.

For further information on NFSv4 delegation, please see "Managing Network File Systems in Oracle® Solaris 11.2" in the Solaris product documentation.

References

<BUG:14192514> - EXALOGIC: NFS4 MOUNT POINT HANG DUE TO ZFS NFS4 DELEGATION LOOP
<BUG:22287161> - CONSOLIDATION HANGS LOGGING TO NFS VERSION 4
<BUG:13978004> - STRESS --> PROCESSES HANG TRYING TO ACCESS STORAGE
<NOTE:1481713.1> - NFSv4 mount directories hang on Exalogic Machine
<NOTE:1019887.1> - Sun Storage 7000 Unified Storage System: How to Collect a Support Bundle using the BUI or CLI
<NOTE:1924941.1> - Exalytics and ZFSSA Configuration over 10g and HBA Interfaces
<BUG:23010051> - EXALYTICS T5-8: HANGS USING HFM APPLICATIONS WITH ZFS AND NFSV4 DELEGATION

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