Creating a switchable independent disk pool

 

Before you attempt to do switchable independent disk pools, ensure that you have satisfied the hardware, software, communications, and physical planning requirements.

iSeries™ Navigator is the recommended interface for creating and managing independent disk pools. Wizards in the clusters and disk management components simplify the tasks and guide you through the process. For some disk management tasks, iSeries Navigator is the only option. Make sure you have fulfilled the iSeries Navigator requirements for disk management.

After an expansion unit (frame/unit) is configured as switchable, the disk units in these resources cannot be used in independent disk pools that span different Cluster Resource Groups (CRGs). Even when only one node is defined and no switching will actually be enabled, configuring that expansion unit as switchable is enough to cause this constraint to be enforced. To create a switchable independent disk pool using iSeries Navigator, do the following steps:

1. Create a cluster. To use switchable independent disk pools, a cluster is required.

2. Make your hardware switchable. If you have a stand-alone expansion unit or an IOP that contains disk units that are to be included in an independent disk pool, authorize the expansion unit or IOP to grant access to other nodes.

3. Create a switchable hardware group. A switchable hardware group, also known as a device CRG, defines the switchable independent disk pool. This is what manages the switching of the device. This wizard takes you through the steps to create a new switchable hardware group. It will also guide you through the New Disk Pool wizard which will assist you in creating a new disk pool and adding disk units to it for the cluster.

   If you had switchable software products which conform to specific iSeries Navigator cluster guidelines installed when you ran the New Cluster wizard in step 1, the New Cluster wizard may have already prompted you to create a switchable hardware group. If the New Cluster wizard did not detect that a switchable software product was installed, then you have not created the switchable hardware group.

4. Print your disk configurations. Print your disk configuration to have in case a recovery situation occurs. Also, record the relationship between the independent disk pool name and number.

You have now created a switchable independent disk pool. To prepare it for use, do the following steps:

1. Start the switchable hardware group to enable device resiliency for the switchable hardware group.

2. Make a disk pool available. To access the disk units in an independent disk pool make the disk pool available (vary on) the disk pool.

3. Perform a test switchover. Before you add data to the disk pool, perform a test switchover on the switchable hardware group you created to ensure the configuration functions as you planned.

You can also use CL commands and APIs for creating a switchable independent disk pool, however, there are some tasks that require that you use iSeries Navigator. To configure your geographic mirroring with the CL commands and APIs, follow these steps:

1. Create the cluster with the nodes that you want using the CRTCLU (Create Cluster) command.

2. Start the nodes in the cluster using the STRCLUNOD (Start Cluster Node) command.

3. Create the device domain. You must create the device domain for all nodes involved in switching an independent disk pool using the ADDDEVDMNE (Add Device Domain Entry) command.

4. Create the device descriptions. Device descriptions must be created on each node that will be in the cluster resource group (CRG). Use the CRTDEVASP (Create Device Description (ASP) command. On the command line in the character-based interface, enter CRTDEVASP. In the Resource Name and the Device Description fields, enter the name of the independent disk pool you plan to create.

5. Create the cluster resource group. Create the device CRG with the nodes, their roles in the recovery domain, and the independent disk pool device descriptions. You must also specify a site name and data port IP addresses for each node in the recovery domain. Use the CRTCRG (Create Cluster Resource Group) command.

6. Make your hardware switchable. If you have a stand-alone expansion unit or an IOP that contains disk units that are to be included in an independent disk pool, authorize the expansion unit or IOP to grant access to other nodes (iSeries Navigator required).

7. Create a disk pool on the node that owns the disk units using the New Disk Pool wizard when the system is fully restarted. Make sure clustering is active before you start. Name the independent disk pool to match the device description resource name. As you add disk units, it is best to localize disk units in the same expansion unit or IOP. Also, do not spread the disk pool across parity sets than necessary.

8. Print your disk configuration in case of a recovery situation. See how to display your disk configuration in Backup and Recovery. Also, record the relationship between the independent disk pool name and number.

9. Start the cluster resource group to enable device resiliency using the STRCRG (Start Cluster Resource Group) command.

10. To access the disk units in an independent disk pool, vary on the disk pool using the VRYCFG (Vary Configuration) command.

11. Before you add data to the disk pool, use the CHGCRGPRI (Change CRG Primary) command to perform a test switchover. Use the test switchover to ensure the backup node can become the primary node and the primary node can become the backup node. .

Specifying a recovery time for the independent disk pool

To improve the vary on performance after an abnormal vary off, consider specifying a private customized access path recovery time specifically for that independent disk pool via the Change Recovery for Access Paths (CHGRCYAP) command rather than relying upon the overall system-wide access path recovery time. This will limit the amount of time spent rebuilding access paths during the vary on.

• Creating a cluster
  For an independent disk pool to be switchable among systems or for geographic mirroring to be enabled, a cluster is required.

• Creating a switchable hardware group
  Create a switchable hardware group, also known as a device cluster resource group (CRG).

• Starting a switchable hardware group
  To enable device resiliency for the switchable hardware group, start the switchable hardware group. Use the steps to start a switchable hardware group.

• Creating an independent disk pool
  You can create a new independent disk pool and add disk units to it. You can also add disk units to an existing disk pool.

• Making your hardware switchable
  In a multisystem environment, make an external expansion unit switchable.

• Synchronizing user profile name, UID, and GID
  Synchronize user profiles across your cluster to reduce the amount of processing required when you make a disk pool available.

• Switching access to backup system
  Perform a cluster switchover when you want a backup system to access the switchable device containing an independent disk pool.

• Changing the system takeover IP address
  Change the IP address for a system associated with a relational database in a clustered, switchable environment.

 

Parent topic:

Configuring independent disk pools

Related concepts
Planning for independent disk pools Creating a switchable hardware group Independent disk pools with distinct databases Scenario: Consolidating systems using switchable independent disk pools

Related tasks
Creating a cluster Making your hardware switchable Printing your disk configuration Starting a switchable hardware group Making a disk pool available Creating a new disk pool group

Related information
Performing a test switchover CRTCLU (Create Cluster) Command STRCLUNOD (Start Cluster Node) Command ADDDEVDMNE (Add Device Domain Entry) command CRTDEVASP (Create Device Description (ASP)) Command CRTCRG (Create Cluster Resource Group) Command Backup and Recovery STRCRG (Start Cluster Resource Group) Command VRYCFG (Vary Configuration) command CHGCRGPRI (Change CRG Primary)