Upgrading ELK stack from 5.5.1 to 6.6.1

In IBM Cloud Private 3.2.1 release, the ELK stack is upgraded from version 5.5.1 to 6.6.1. The upgrade process is transparent to users.

• For managed-mode logging instances, the IBM Cloud Private 3.2.1 upgrade process automatically handles Elastic binary upgrade, configuration update, and data migration.
• For standard-mode logging instances, a similar process occurs when you upgrade the Helm release to the IBM Cloud Private logging chart included in the IBM Cloud Private 3.2.1 catalog.

Automatic upgrade and rollback process

Since Elasticsearch data format is not compatible between major versions, an automatic data migration process runs during upgrade. This process applies to IBM Cloud Private logging instances in both managed and standard modes. By default, on each Elasticsearch data pod, the upgrade process includes the following actions.

• Makes a copy of old index data to <data-pod-pv>/6.x.
• Migrates data to <data-pod-pv>/6.x.
• Leaves existing data intact.

For each data pod, a success flag file is touched under <data-pod-pv>/MIGRATIONCOMPLETE when Elasticsearch data migration completes. This flag makes sure that data is migrated only one time.

You might want to roll back to IBM Cloud Private logging that is included in IBM Cloud Private 3.2.0 and lower. In this situation, the old logging data that is on the logging data PVs is used if the old data is left undeleted.

In addition to Elasticsearch data migration, the Kibana index data schema changed. A migration job is started as part of the upgrade process and is transparent to the user.

Disk space requirements

The disk space requirements that are needed for upgrade include a minimum of 10 GB of disk space after data copying. For example, before you upgrade, your existing disk space might be 100 GB. A total of 210 GB of disk space is needed on the PV of each Elasticsearch data pod.

100 GB (existing data) + 100 GB (6.x data copy) + 10GB (required spare space) = 210 GB (total required disk space)

Notes:

• Check the disk space before you upgrade. Allocate more storage as needed.
• The IBM Cloud Private logging instance does not start if you do not assign enough disk space.
• Two other options are available that require less disk space. For more information, see Customizing upgrade behaviors

Customizing upgrade behaviors

You can change the following chart parameters to customize your IBM Cloud Private logging upgrade behavior.

 upgrade:
   elasticsearch:
     # set to true if data from old version needs to be imported
     importData: true
     # if set to true, a copy of existing data in old format will be left intact
     # under pv-mount/nodes (/usr/share/elasticsearch/data/nodes)
     # this allows data (up to point of upgrade) to be restored when rolling back
     retainOldData: true

The following options can reduce your disk requirements. Set these values to change the default upgrade behavior.

• Set upgrade.elasticsearch.importData to false when you want a fresh empty data store. No existing data is available in your upgraded system.

• Set upgrade.elasticsearch.retainOldData to false when you want existing data to be deleted after the upgrade process.

  Important: If you roll back to an earlier version, your old data is not available.