3.7.0 HP StorageWorks HP Scalable NAS File Serving Software provisioning guide for Oracle HP Scalable NAS (AG513-96013, October 2009)

for all Oracle versions prior to 10.2.0.4, it is necessary to configure Oracle on the
NFS client systems to use direct IO and not asynchronous I/O. Fortunately, this bug
was fixed at version 10.2.0.4. All others should consider using asynchronous I/O
as well as direct I/O. The instructions in this guide assume that you are using direct
I/O.
When you locate data files on an NFS mount that is exported from a filesystem
mounted as dboptimized in the NFS server, you will definitely want to use direct IO
if your OS platform allows it (most do).
In the following example for Red Hat Linux, this line in init.ora would select direct
IO without async IO:
filesystemio_options = directIO
For NFS clients such as Red Hat 5.2 running Oracle Server 10.2.0.4 or greater, you
can specify direct IO and async IO using this entry:
filesystemio_options = setall
If you decide to use async IO for Linux Oracle server systems over NFS, have your
System Administrator keep a close watch on the use of /proc/sys/fs/aio-nr
on your Oracle server. The maximum allowed for this is set in /proc/sys/fs/
aio-max-nr, and the default is quite low (64k). It would be prudent for your System
Administrator to set this much higher (for example, 512k) and watch the actual use
carefully.
Database writer processes
For write-intensive workloads, it may be necessary to increase the number of Database
Writer processes. Not to be confused with Database Writer I/O slaves, multiple
Database Writers are an efficient way to configure Oracle so that modified SGA
buffers can be efficiently flushed to the PSFS filesystem. A general rule to follow is to
configure four Database Writer processes per processor on the NFS client. On
dual-core processors, that number should be doubled.
For instance, an NFS client with four dual-core processors would have the init.ora
parameter for db_writer_processes configured as follows:
db_writer_processes = 32
Configured as such, the NFS client will be able to perform as many as 32 concurrent
synchronous writes to the PSFS filesystems per second. The free buffer waits statistic
should be monitored to see if the Database Writer processes are able to keep up
sufficiently with the workload. If the number of free buffer waits becomes one of the
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