3 Using Shared Storage

This chapter provides basic recommendations for using shared storage in a high availability environment. It describes the benefits of placing artifacts in a common location that multiple hosts or servers share. This common location typically resides in a shared file system, which is mounted on each server with standard operating system protocols such as NFS and CIFS.

The following artifacts are typical candidates to place on a shared file system:

This chapter includes the following topics:

3.1 Overview of Shared Storage

Shared storage allows sharing of dynamic state and server configuration and simplifies administration, configuration, failover, and backup/recovery.

In a highly available environment, shared storage is required when using file based persistence stores (for JMS and JTA logs) and certain Oracle products. Shared storage is optional for product binaries and domain directories.

See Table 3-1 for additional information about shared storage.

Table 3-1 Shared Storage Topics

Topic/Task For More Information

Structure and contents of an Oracle home

"Understanding the Oracle Fusion Middleware Infrastructure Directory Structure" in Oracle Fusion Middleware Installing and Configuring the Oracle Fusion Middleware Infrastructure

Saving JMS and JTA information in a file store

"Using the WebLogic Persistent Store" in Administering Server Environments for Oracle WebLogic Server. Includes the topic "High Availability for Persistent Stores"

"Persistent Store High Availability" in Administering JMS Resources for Oracle WebLogic Server

Default File Store Availability for JTA in Administering Clusters for Oracle WebLogic Server

3.2 Shared Storage Prerequisites

The following shared storage prerequisites apply only when you use file-based persistent stores:

  • For proper recovery in the event of a failure, you must store both JMS and JTA transaction logs in a location that is accessible to all nodes that can resume operations after a Managed Server failure. This setup requires a shared storage location that multiple nodes can reference. See Section 3.6, "Directory Structure and Configurations" for the recommended directory structure.

  • The shared storage can be a network-attached storage (NAS) or storage area network (SAN) device. For NFS-mounted systems, issues related to file locking and abrupt node failures have been detected. Check the Oracle Fusion Middleware Release Notes and with your storage vendor for the main recommended parameters for mount options.

    The following example command is based on a NAS device. Note that your options may be different from those in this example; see UNIX/Linux documentation for more information on the mount command and its options.

    mount nasfiler:/vol/vol1/u01/oracle /u01/oracle -t nfs -o rw,bg,hard,nointr,tcp,vers=3,timeo=300,rsize=32768,wsize=32768

  • For maximum availability, Oracle recommends a highly available NAS or SAN device for shared storage. Shared storage devices that are not highly available can be a single point of failure. Check with your storage provider for options to achieve this.

For more information about saving JMS and JTA information in a file store, see "Using the WebLogic Persistent Store" in Administering Server Environments for Oracle WebLogic Server.

3.3 Using Shared Storage for Binary (Oracle Home) Directories

The following sections describe guidelines for using shared storage for your Oracle Fusion Middleware Oracle home directories:

3.3.1 About the Binary (Oracle Home) Directories

When you install any Oracle Fusion Middleware product, you install the product binaries into an Oracle home. The binary files are read-only and do not change unless the Oracle home is patched or upgraded to a newer version.

In a typical production environment, the Oracle home files are saved in a separate location from the domain configuration files, which you create using the Oracle Fusion Middleware Configuration Wizard.

The Oracle home for an Oracle Fusion Middleware installation contains the binaries for Oracle WebLogic Server, the Oracle Fusion Middleware infrastructure files, and any Oracle Fusion Middleware product-specific directories.

Note:

By default, the Configuration Wizard writes its logs to the logs directory in Oracle home. If you use a read-only Oracle home, you must specify the -log option to redirect logs to a different directory.

See Also:

For more information about the structure and contents of an Oracle home, see "What are the Key Oracle Fusion Middleware Directories?" in Oracle Fusion Middleware Understanding Oracle Fusion Middleware Concepts.

3.3.2 About Using Redundant Binary (Oracle Home) Directories

For maximum availability, Oracle recommends using redundant binary installations on shared storage.

In this model, you install two identical Oracle homes for your Oracle Fusion Middleware software on two different shared volumes. You then mount one of the Oracle homes to one set of servers and the other Oracle home to the remaining servers. Each Oracle home has the same mount point, so the Oracle home always has the same path, regardless of which Oracle home the server is using.

If one Oracle home become corrupted or unavailable, only half your servers are affected. For additional protection, Oracle recommends that you disk mirror these volumes.

If separate volumes are not available on shared storage, Oracle recommends simulating separate volumes using different directories within the same volume and mounting these to the same mount location on the host side. Although this does not guarantee the protection that multiple volumes provide, it does allow protection from user deletions and individual file corruption.

3.4 Using Shared Storage for Domain Configuration Files

The following sections describe guidelines for using shared storage for the Oracle WebLogic Server domain configuration files you create when you configure your Oracle Fusion Middleware products in an enterprise deployment:

3.4.1 About Oracle WebLogic Server Administration and Managed Server Domain Configuration Files

When you configure an Oracle Fusion Middleware product, you create or extend an Oracle WebLogic Server domain. Each Oracle WebLogic Server domain consists of a single Administration Server and one or more Managed Servers.

WebLogic uses a replication protocol to push persisted changes on the Administration Server to all Managed Servers. This gives redundancy to the Managed Servers so that you can start them without the Administration Server running. This mode is called Managed Server independence.

For more information about Oracle WebLogic Server domains, see Understanding Domain Configuration for Oracle WebLogic Server.

3.4.2 Shared Storage Considerations for Administration and Managed Server Domain Configuration Files

This section describes considerations for Administration Server and Managed Server configuration files.

Administration Server Configuration Directory

Oracle does not require that you store domain configuration files in shared storage. However, to support Administration Server recovery, you may choose to place the Administration Server configuration directory on shared storage and mount it on the host that is running the Administration Server. If that host fails, you can mount the directory on a different host and bring up the failed Administration Server on the other host.

Managed Server Configuration Files

Oracle recommends that you keep the Managed Server configuration files in local, or, host private, storage.

It is possible to keep Managed Server configuration files on shared storage. However, doing so can affect performance due to multiple servers concurrently accessing the same storage volume.

3.5 Shared Storage Requirements for JMS Stores and JTA Logs

When you use file-based persistence, it is mandatory to configure the JMS persistence stores and JTA transaction log directories to be in shared storage. For more information, see Section 5.4, "Considerations for Using File Persistence (WebLogic JMS)."

3.6 Directory Structure and Configurations

When you use shared storage, there are multiple ways to layout the storage elements. Oracle recommends the following best practices:

  1. Place the product binaries (Oracle home) on shared storage and share it in a read-only mode by all servers.

  2. Place the Administration Server domain configuration directory on shared storage to facilitate failing over the Administration server to a different host.

  3. Place each Managed Server domain configuration directories on storage local to the corresponding host.

  4. Place the JMS file stores and Transaction logs on shared storage if you use file-based persistence.

Figure 3-1 illustrates the directory structure.

Items that have arrows on both sides showing that they are connected to both nodes indicate the directories on shared storage. If Node 1 fails, the Administration Server domain directory is mounted on Node 2 (see the dotted arrow) to failover the Administration Server to Node 2.

Figure 3-1 Shared Storage Directory Structure

The text that precedes this graphic describes it.
Description of "Figure 3-1 Shared Storage Directory Structure"