Kevin Closson's Blog: Platforms, Databases and Storage

Recently, a participant on the oracle-l email list asked the following question:

Per note 359515.1 nfs mounts are supported for datafiles with oracle 10. Does anyone know if the same applies for 9.2 databases?

I’d like to point out a correction. While Metalink note 359515.1 does cover Oracle10g related information about NFS mount options for various platforms, that does not mean Oracle over NFS is limited to Oracle10g. In fact, that couldn’t be further from the truth. But before I get ahead of myself I’d like to dive in to the port-level aspect of this topic.

There are no single set of NFS mount options that work across all Oracle platforms. In spite of that fact, another participant of the oracle-l list replied to the original query with the following:

try :
rw,bg,vers=3,proto=tcp,hard,intr,rsize=32768,wsize=32768,forcedirectio

OK, the problem is that of the 6 platforms that support Oracle over NFS (e.g., Solaris, HP-UX, AIX, Linux x86/x86_64/AI64), the forcedirectio NFS mount option is required only on Solaris and HP-UX. For this reason, I’ll point out that the best references for NFS mount options to use for Oracle10g is Metalink 359515.1 and NAS vendors’ documents for Oracle9i.

Oracle9i
Support for Oracle9i on NFS was a little spottier than Oracle10g, but it was there. The now defunct Oracle Storage Compatibility Program (OSCP) was very important in ensuring Oracle9i would work with varying NAS offerings. The Oracle server has evolved nicely to handle Oracle over NFS to such a degree that the OSCP program is no longer even necessary. That means that Oracle10g is sufficiently robust to know whether the NFS mount you are feeding it is valid. That aside, the spotty Oracle9i support I allude to is actually at the port level mostly. That is, from one port to another, Oracle9i may or may not have required patches to operate efficiently and with integrity. One such example is the Oracle9i port to Linux where Oracle Patch number 2448994 was necessary so that Oracle would open files on NFS mounts with the O_DIRECT flag of the open(2) call. But, imagine this, it was not that simple. No, you had to have the following correct:

• The proper mount options specified by the NAS vendor
• A version of the Linux kernel that supported O_DIRECT
• Oracle patch 2448994
• The Correct setting for the filesystemio_options init.ora parameter

Whew, what a mess. Well, not that bad really. Allow me to explain. Both of the Linux 2.6 Enterprise kernels (RHEL 4, SuSE 9) support open(2)s of NFS files with the O_DIRECT. So there is one requirement taken care of—because I assume nobody is using RHAS 2.1. The patch is simple to get from Metalink and the correct setting of the filesystemio_options parameter is “directIO”. Finally, when it comes to mount options, NAS vendors do pretty well documenting their recommendations. Netapp has an entire website dedicated to the topic of Oracle over NFS. HP EOMs the File Serving Utility for Oracle from PolyServe and documents their mount options in their User Guide as well as in this paper about Oracle on the HP Clustered Gateway NAS.

Oracle10g
I’m not aware of any patches for any Oracle10g port to enable Oracle over NFS. I watch the Linux ports closely and I can state that canned, correct support for NFS is built in. If there were any Oracle10g patches required for NFS I think they’d be listed in Metalink 359515.1 which, at this time, does not specify any. As far as the Linux ports go, you simply mount the NFS filesystems correctly and set the init.ora parameter filesystemio_options=setall and you get both Direct I/O and asynchronous I/O.