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Before the dNFS driver is configured or used on an NFS share, the NFS share must first be mounted using the kNFS driver. Specific mounting options are required when mounting an NFS share for Oracle usage. If the NFS export will be used for Oracle services that need to be automatically restarted when the server restarts, add the NFS export and mount options to /etc/fstab. If the NFS share and mount options are not specified in /etc/fstab, Oracle will experience issues. In an Oracle RAC cluster, ensure that all nodes in the cluster use the same mount options and /etc/fstab entry for each identical NFS share mount point.
After the NFS share is mounted using kNFS, dNFS mounts and unmounts the NFS share logically as needed. Because dNFS uses a logical mount, after Oracle unmounts the NFS share, the NFS share is still physically mounted to the server and can be accessed through kNFS.
If NFS is used for database files, the NFS buffer size for reads (rsize) and writes (wsize) must be set to at least 16,384. Oracle recommends a value of 32,768. These values are set in /etc/fstab or when explicitly mounting an NFS share. For performance reasons, Dell Technologies recommends evaluating whether rsize and wsize should be changed from the Oracle default.
PowerStore NAS servers support a range of values for rsize and wsize in 8 KiB increments starting from 8192 to 1048576, with a default 262144 for both rsize and wsize. dNFS clients issue writes with (v$dnfs_servers.wtmax) granularity to the PowerStore NAS server.
Note: Changing the rsize or wsize on the PowerStore NAS server requires a restart of the PowerStore appliance.
The required mount options for NFS share mount points used by Oracle are:
rw,bg,hard,nointr,rsize=32768,wsize=32768,tcp,nfsvers={3|4},timeo=600,actimeo=0
rw,bg,hard,nointr,rsize=32768,wsize=32768,tcp,nfsvers={3|4},timeo=600,actimeo=0,noac
Note: Mount option actimeo=0 is required only for Oracle RAC and certain Oracle components (for example: GoldenGate binaries and datafiles). For more information, see Oracle documentation or Oracle Support MOS notes.
When configuring an Oracle RAC environment that uses NFS, ensure that the entry in /etc/fstab is the same on each node. The following snippet from /etc/fstab mounts an NFS mount point for ORACLE_HOME binaries (/u01), and a RAC database that will use ASM.
zzz.zzz.zzz.zzz:/ora-bin /u01 nfs rw,bg,hard,nointr,rsize=32768,wsize=32768,tcp,vers=3,timeo=600,actimeo=0,defaults 0 0
uuu.uuu.uuu.uuu:/ORA-ASM-NFS /oraasmnas nfs rw,bg,hard,nointr,rsize=32768,wsize=32768,tcp,vers=3,timeo=600,actimeo=0,defaults 0 0
When specifying mount options, do not include spaces between options because the operating system might not properly parse the options.
Mount options timeo, hard, soft, and intr control the NFS client behavior if the NFS server becomes temporarily unreachable. Whenever the NFS client sends a request to the NFS server, it expects the operation to have finished after a given interval (specified in the timeout option). If no confirmation is received within this time, a minor timeout occurs, and the operation is retried with the timeout interval doubled. After a maximum timeout of 60 s is reached, a major timeout occurs. By default, a major timeout causes the NFS client to print a message to the console and start over with an initial timeout interval twice that of the previous cascade. Potentially, this action could be repeated indefinitely. Volumes that retry an operation until the server becomes available again are called hard-mounted.
For additional mount options and information about using NFS shares intended for Oracle, see the Oracle MOS notes listed in References.