Partitions with Forest-Level Failover
The partition create, migrate and resize operations allow you to specify an options element to create replica forests for shared-disk or local-disk failover, as described in the Configuring Local-Disk Failover for a Forest and Configuring Shared-Disk Failover for a Forest in the Scalability, Availability, and Failover Guide.
To create replica forests for forest-level failover, you must create the partition on at least two hosts. For each master forest created on one host a replica forest will be created on another host. For example, to create a single replica forest for each forest in the 2011 range partition and configure the forests for local-disk failover between MyHost1, MyHost2, and MyHost3, use these scripts:
$ cat create-partition.xml <partition xmlns="http://marklogic.com/manage"> <partition-name>2011</partition-name> <upper-bound>2012-01-01</upper-bound> <lower-bound>2011-01-01</lower-bound> <forests-per-host>4</forests-per-host> <data-directory>/forests</data-directory> <hosts> <host>MyHost1</host> <host>MyHost2</host> <host>MyHost3</host> </hosts> <data-directory></data-directory> <large-data-directory></large-data-directory> <fast-data-directory></fast-data-directory> <options> <option>replicas=1</option> <option>failover=local</option> </options> </partition>
$ curl --anyauth --user user:password -X POST \ -d @create-partition.xml -H 'Content-type: application/xml' \ http://MyHost:8002/manage/v2/databases/Documents/partitions
Keep in mind the following details when configuring partitions or forests with forest-level failover:
If failover is configured on your forests, do a full backup of database after doing a partition or forest migrate or a forest combine to ensure that you can recover your data should something go wrong. You may also need to increase the timeout setting on the migrate or combine operation, as these operations will take longer when failover is configured.
It is not recommended to configure local-disk failover for forests attached to a database with journaling set to
off.You cannot configure a partition with shared-disk or local-disk failover on Amazon Simple Storage Service (S3), unless its fast data directory, as designated by
<fast-data-directory>, is not on S3.If your deployment of MarkLogic is on Amazon Elastic Compute Cloud (EC2) or is distributed across multiple data centers, be sure to specify an equal number of hosts on different zones when creating, migrating, or resizing your partition with forest-level failover. For example, two hosts on
us-east-1a, two hosts onus-east-1b, and two hosts onus-east-1c. In this example, tiered storage will ensure that master and their replica forests are created on hosts in different zones. This ensures that the partition will remain accessible should a forest, host, or entire zone go down.