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PSFS File System

Oracle RAC Cluster Tips by Burleson Consulting

This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters.  To get immediate access to the code depot of working RAC scripts, buy it directly from the publisher and save more than 30%.

PSFS is a general-purpose cluster file system. It is an enterprise-grade symmetric file system. The general features include:

* PSFS allows Oracle Managed Files (OMF) to be used in an Oracle RAC cluster. Oracle OMF provides the ability to manage files and file systems that reduces the complexity of creating, configuring, and managing the storage for an Oracle database. Oracle9i RAC with a shared raw device cannot use OMF functionality.

* All matrix server members have access to the file system and can perform concurrent read/write operations.

* Supports Direct I/O facility, which increases the I/O performance by avoiding the file system buffering

* The Oracle Disk Manager (ODM). ODM is an API specification for I/O designed by Oracle. PolyServe?s ODM offering, MxODM, is a plug-in module for PolyServe?s cluster file system. MxODM comes bundled with either the Oracle RAC Option or Oracle Option for Matrix Server.

* Device Naming and Utilities ? Cluster-wide device naming and file system utilities simplify administration and maintenance of the cluster. MxS provides a pseudo device layer that ensures consistent device naming across the cluster, and provides various tools for file system maintenance, including fsck, file system suspend, and resume and file system growth.

* PSFS also supports context dependant symbolic links that allow administrators to configure node-specific files.

* MxS supports all Oracle data files and logs and further supports advanced Oracle9i functionality, including external tables, export/import from text files, and archived redo log compression.

* MxS also supports a shared Oracle Home, which simplifies installation, configuration, and maintenance.

* It is a standard Linux File system that supports file system operations such as mkfs, mount and unmount and byte-range locking with complete cache coherency.

PolyServe MxS uses a registry to control server access to the PSFS file system on the SAN disks imported into the matrix. It supports journaling and online crash recovery.

PSFS supports context dependent symbolic links (CDSL). CDSL are used to manage node-specific files and directories. CDSL(s) enable database administrators to easily create an Oracle Home directory that can be shared by all nodes in the matrix.

CDSL contains a keyword that identifies a particular location. When the operating system resolves the symbolic link, it translates the keyword into the appropriate pathname. For example, a CDSL could contain the keyword HOSTNAME, which resolves the hostname of the server where it has been logged in.

Configure and Create PSFS

The PSFS file system is created on a storage extent located on imported disks. Storage extents are disk partitions. The maximum file system is 1 TB. PSFS uses 4KB as the block size.

A file system can be created using either the management console or the command line. Then, the file system can be mounted on all the nodes or servers in the matrix. Since the disk partition is the unit on which the file system is created, plan the size of the partition carefully.

To create a file system using the CLI, use the PolyServe command:

# mx fs create [--size <kb>] <filesystem> <StorageExtent>


# mkpsfs <device> [<size_in_blks>]

Where the global device name is specified as /dev/psd/psdXXXpYY where XXX is the disk number and YY is the partition number. Then, mount the PSFS file system on any server in the matrix. Use the Polyserve MxS command:

# mx fs mount [--persist] [--activate] [--options] <path> <filesystem>


Or use the usual Linux command with option ?t:

# mount ?t psfs ?o options <device> <mountpoint>

When using the PolyServe mount command, the persist option can be used for the file system to mount automatically whenever the server is rebooted. To see the status of the file system, use the PolyServe command:

# mx fs status [--mounted] [--persistent] [--verbose]


This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters, Rampant TechPress, by Mike Ault and Madhu Tumma.

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.


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