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User-managed file system support for Db2 pureScale environments

Although a file systems that is managed by the Db2 product is recommended, you might want to use your existing shared file system.

Currently, the only supported user-managed file system is an IBM® Spectrum Scale file system. For the supported IBM Spectrum Scale versions, see the Installation prerequisites for Db2 pureScale Feature (AIX). During product installation, the Db2 installer checks whether the version of the user-managed IBM Spectrum Scale cluster and file system is supported. If it is not supported, instance creation fails.

In addition to ensuring that you are using the correct version, you must verify your existing IBM Spectrum Scale file system configuration. To verify the configuration of the current file system cluster, issue the following command:
   install_path/bin/db2cluster -cfs -list –filesystem
where install_path is the current file system cluster location.
To verify the file system setup, issue the following command:
   install_path/bin/db2cluster -CFS -VERIFY -CONFIGURATION -FILESYSTEM db2fs1
where mygpfs1 is the name of the existing IBM Spectrum Scale cluster file system.

A Db2 managed file system and a user-managed file system cannot coexist. The IBM Db2 pureScale Feature supports only one Db2 pureScale instance; you use either a Db2 managed file system or a user-managed file system.

If you use a user-managed file system, the default passwordless remote root login is required.

When you create your first Db2 pureScale instance, you must provide the full path to an existing IBM Spectrum Scale file system to indicate that you want to use a user-managed file system. The Db2 installer verifies that the file system is valid to use.

For response file installations, the INSTANCE_SHARED_DEVICE_PATH keyword represents a Db2 managed file system. The INSTANCE_SHARED_DIR keyword can represent either a user-managed file system or a Db2 managed file system. If you create a Db2 managed file system by using the db2cluster_prepare command, you can use the INSTANCE_SHARED_DIR keyword for either a Db2 managed file system or a user-managed file system.

In a Db2 Setup wizard installation, the Set up a Db2 Cluster File System Panel panel detects the cluster environment.

For the db2icrt or db2iupdt command, the -instance_shared_dev option represents a Db2 managed file system. The -instance_shared_dir option can represent either a user-managed file system or a Db2 managed file system. If you create a Db2 managed file system by using the db2cluster_prepare command, you can use the —INSTANCE_SHARED_DIR keyword for either a Db2 managed file system or a user-managed file system, as in the following example:
   db2icrt -d
           -cf host1:host1-ib0
           -m host2:host2-ib0
           -instance_shared_dir mygpfs1
           -tbdev /dev/hdisk2
           -u db2sdfe1
           db2insd1

In this example, the same IBM Spectrum Scale cluster is set up on both host1 and host2, and the mygpfs1 file system is mounted on both of them. The mygpfs1 file system is the mount point of the existing IBM Spectrum Scale cluster file system. The host names of host1 and host2 must match the host names that are configured on the IBM Spectrum Scale cluster. The existing instance owner user, db2insd1, must have write access to the mygpfs1 directory from both host1 and host2. Because a user-managed file system is being used, the -instance_shared_dir parameter is specified rather than the -instance_shared_dev parameter.

When extending the Db2 pureScale instance to a remote host, first extend the cluster to the remote host and set up the host to have write access as root to the file system first. The Db2 installer performs the corresponding validation, as in the following example:
   db2iupdt -d -add -m host3:host3-ib0 db2insd1

In this example, running the command extends the instance to a new member, host3. This host must be included in the same IBM Spectrum Scale cluster that has host1 and host2. The mygpfs1 file system must be mounted from host3. The instance owner, db2insd1, must have write access to the mygpfs1 file system.

The Db2 installer and the instance commands do not change the IBM Spectrum Scale cluster during the following actions:
  • The creation of a Db2 pureScale instance
  • The extension of a Db2 pureScale instance
  • The dropping of a Db2 pureScale instance
  • The dropping of a member or cluster caching facility from the instance

Spectrum Scale Cluster Configuration Repository (CCR) Setting

CCR is the default cluster configuration repository type for any new and upgraded pureScaleinstances provided the prerequisite package 'gpfs.gskit' is installed. This repository type provides better highavailability and simpler cluster configuration setup with lower administration overhead. The current CCR setting can bequeried with the following command:

db2cluster -cfs -list -configuration

Sample output for a CCR enabled cluster is shown below.

$ db2cluster -cfs -list -configuration
OPTION                          VALUE
------------------------------ ---------------------------------
adminMode                       allToAll  
.  
.  
.  
tracedevBufferSize              67108864  
afmHashVersion                  1
ccrEnabled                      yes  
remoteShellCommand              /usr/bin/ssh  
remoteFileCopyCommand           /usr/bin/scp

If the value is set to 'no', ensure the prerequisite package 'gpfs.gskit' is installed on all hosts in the cluster first before

enabling CCR manually with the following command (note that the cluster must not be in maintenance mode and quorumnodes in the cluster must be online for the enablement to succeed):

db2cluster -cfs -set -option ccrEnabled -value yes

Re-run "db2cluster -cfs -list -configuration" to confirm the new setting is in effect. No restart of the Db2 instance is required.