Alternative to NFS: Image and Services on Local Disk with WebLogic Feature Pack

Intended for use with WebLogic Feature Pack V2.3.

The Cassatt Active Response document Alternative to NFS: Images on Local Disk describes how to configure Cassatt Active Response to boot images from local disk for sites that discourage use of NFS. Read this document to understand how images work on local disk and how managing your WebLogic image is different when you boot from local disk.

When using WebLogic Feature Pack, if you opt to boot WebLogic images from local disk, any service that uses the image is also installed on local disk. That is, you can't install images on local disk but not services.

You can, however, use a manual variation on local disk installation for services without using local installation for images. Read Alternative to the Service Matrix: Domains Installed on the Administration Server.

You can combine the alternative to NFS described here with the alternative to the service matrix described in Alternative to the Service Matrix: Domains Installed on the Administration Server.

Read this sidebar to understand the differences between the two approaches and to understand what happens when you combine these two alternatives.

How it works

When you have configured your WebLogic image to boot from local disk, WebLogic Feature Pack also installs your WebLogic domains on local disk. Each time WebLogic Feature Pack needs to start a domain on a Managed Server, WebLogic Feature Pack checks for the domain on the Administration Server node.

• If the domain is not present (for example, on the very first deployment or if the Administration Server node has been replaced), WebLogic Feature Pack copies the domain from the service matrix onto the Administration Server node.
  
  Be aware that the time required to copy a domain varies; therefore, monitoring is not started until the Administration Server responds to a wget of the domain administration console.
• If the domain is present on the Administration Server's local disk, WebLogic Feature Pack uses those files instead of the files in the service matrix.
  
  In general, services with domains on local disk start about half as fast on the first start as services with domains served from the service matrix because of the time required to copy the domain.

The functionality for WebLogic Feature Pack-installed domains on local disk is very similar to when you install the domain on the Administration Server yourself—as described in Alternative to the Service Matrix: Domains Installed on the Administration Server—and the same caveats apply. In addition: any changes to the domain on the Administration server are lost in the event of a node failure and replacement, and any time you deallocate the WebLogic Administration Server tier.

When you use this alternative, you risk losing important data: whenever the Administration Server node is deallocated from the tier or is replaced because of failure, any changes to the domains on the node are lost. This includes upgrades to domain files (such as WARs or JARs), configuration changes, transactions, JMS messages, and so forth.

Preparing a WebLogic image for local boot when using WebLogic Feature Pack

Follow these steps in conjunction with WebLogic Feature Pack: Capturing an Image and Creating Tiers to configure your WebLogic image to use local disk:

1. During cccapture:
   1. Specify a local disk size that's adequate to hold your WebLogic image plus any domains you will run with the image.
      
      Enter the minimum size in Gbytes for the required local disk [0]:
   2. Change the default (No) to "Yes" to install the image on local disk.
      
      Should this image be installed on the local disk (allowing the node to boot locally)? [n]
   3. Note that ping monitoring is disallowed when the image is installed locally; ping can report nodes as being up before they are ready to be used.
      
      

      Monitor via ping? [n]

   4. Use script monitoring with caution. Simple script monitors that always return true (for example, /bin/true) should be avoided for the same reasons as ping. Instead, use scripts that faithfully reflect the state of your applications or services running on the node.
2. During tier creation for the Administration Server tier, consider the Automatic Move to Maintenance Pool setting. Turn this setting to "Off" if data on local disk is important: all data on local disk is lost when a node is moved to the maintenance pool. Be aware, however, that if the node in the Administration Server tier fails and Automatic Move to Maintenance Pool is off, Cassatt Active Response cannot replace it, and Administration Server operations are compromised until you manually repair the node or move it out of the tier.

Follow these steps to update an image and tier from NFS to local boot.

1. Deactivate and deallocate the Administration Server tier.
2. Set the image properties to local disk:
   
   Images > Requirements: Perform local installation
3. If ping monitoring is set to "On" for the image, set it "Off":
   
   Images > Requirements > OS Monitoring > Ping > uncheck
4. Make sure the local disk size requirement is sufficient to hold your WebLogic image plus any domains you will run with the image.
5. Consider the Automatic Move to Maintenance Pool setting for the tier. Turn this setting to "Off" if data on local disk is important: all data on local disk is lost when a node is moved to the maintenance pool. Be aware, however, that if the node in the Administration Server tier fails and Automatic Move to Maintenance Pool is off, Cassatt Active Response cannot replace it, and Administration Server operations are compromised until you manually repair the node or move it out of the tier.
6. Reallocate and reactivate the Administration Server tier.
   
   Cassatt Active Response installs the image locally and starts WebLogic Feature Pack services as needed to meet the SLAs.
   

Preparing WebLogic Feature Pack services when using local boot for images

You don't need to do anything extra. Just follow the instructions in WebLogic Feature Pack: Setup. When you have chosen to install the WebLogic image on local disk, WebLogic Feature Pack automatically copies the domains onto the WebLogic Administration Server.

WebLogic Feature Pack copies the domains verbatim, including any log files and other carry-over from running prior to capture. Be sure to delete any unneeded files before capturing the domain as a service image.

Managing a WebLogic image that's configured for local boot when using WebLogic Feature Pack

Follow the guidance in Alternative to NFS: Images on Local Disk and in the "Updating a WebLogic image used with WebLogic Feature Pack" section of WebLogic Feature Pack: Image and Service Management.

Always recapture a domain installed on the Administration Server's local disk after making significant changes or, at a minimum, record the changes so you can manually reapply them in the event of a node replacement. Your applications may fail if the Administration Server node fails and is replaced, and the domain copied from the service matrix is out of date.

Managing WebLogic Feature Pack services when using local boot for images

Only a few procedures differ from standard service management as described in WebLogic Feature pack: Image and Service Management:

• Updating a domain – Refer to the "Updating a WebLogic domain" section in Alternative to the Service Matrix: Domains Installed on the Administration Server.
• Removing services – The ccserviceremove command attempts to remove the domain directory from the Administration Server. If it cannot (for example, if the Administration Server is down), the ccserviceremove command fails. If this happens, either bring up the Administration Server or delete the Administration Server tier.

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