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:
Product binaries: All files and directories related to product executables, JAR files, and scripts that install during product installation.
Domain directory: The directory containing the WebLogic Server domains and their configuration.
File-based persistent stores: File-based persistent stores for JMS persistence and JTA transaction logs.
This chapter includes the following topics:
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 persistent stores (for JMS and JTA logs) and certain Oracle products. Shared storage is optional for product binaries and domain directories.
See Table 4-1 for additional information about shared storage.
|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
"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
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 4.6, "Directory Structure and Configurations" for the recommended directory structure.
Oracle recommends that you use a shared storage device that is network-attached storage (NAS) or storage area network (SAN).
If you use NFS-mounted systems, issues related to file locking and abrupt node failures have been detected. See Section 6.4.1, "Considerations for Using File Stores on NFS" and check 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.
The following sections describe guidelines for using shared storage for your Oracle Fusion Middleware Oracle home directories:
When you install any Oracle Fusion Middleware product, you install the product binaries into an Oracle home (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.
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.
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.
Oracle Fusion Middleware enables you to configure multiple servers from a single Oracle home. This allows you to install the Oracle home in a single location on a shared volume and reuse the Oracle home for multiple servers.
If multiple servers on different hosts share an Oracle home, there are some best practices to keep in mind. For example, because the Oracle inventory directory (
oraInventory) is updated only on the host from which the Oracle home was originally installed, Oracle recommends that all subsequent operations you perform on the Oracle home (such as patching and upgrade) be carried out from that original host. If that host is unavailable, ensure that the Oracle inventory is updated on another host before applying patches or upgrades to the Oracle home from the other host.
For more information about
oraInventory, see "Oracle Universal Installer Inventory" in the Oracle Universal Installer Concepts Guide.
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 becomes corrupted or unavailable, only half your servers are affected. For additional protection, Oracle recommends that you disk mirror these volumes. To restore the affected servers to full functionality, you can simply remount the surviving Oracle Home.
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 protect from user deletions and individual file corruption.
For maximum protection, Oracle recommends that you evenly distribute the members of a cluster across redundant binary Oracle homes. This is particularly important if cluster members are not running on all available servers.
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:
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.
This section describes considerations for Administration Server and Managed Server configuration files.
Oracle does not require that you store domain configuration files in shared storage. However, to support Administration Server recovery, you must 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. For more information, see Chapter 8, "Administration Server High Availability."
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.
When you use file-based persistence in a high availability setup, you must configure the JMS persistent stores and JTA transaction log directories to reside in shared storage. For more information, see Section 6.4, "Considerations for Using File Persistence (WebLogic JMS)."
When you use shared storage, there are multiple ways to lay out the storage elements. Oracle recommends the following best practices:
Share in read-only mode by all servers.
JMS file stores and Transaction logs
Place on shared storage if you use file-based persistence.
Administration Server domain configuration directory
Place in shared storage to facilitate failing over the Administration server to a different host.
Place Managed Server domain configuration directories on storage that is local to the corresponding host. See Section 4.4.2, "Shared Storage Considerations for Administration and Managed Server Domain Configuration Files" for more information.
Figure 4-1 illustrates the directory structure.