Volume Upgrades

MapR supports two types of volumes: read-write and mirror (read-only). The concept of promoting a mirror refers to the ability to make a read-only mirror volume into a read-write volume. The main use case for this feature is to support disaster-recovery scenarios in which a read-only mirror needs to be promoted to a read-write volume so that it can become the primary volume for data storage. You can also convert read-write volumes back to read-only mirrors.

The feature that allows mirror volumes to be promoted to read-write was introduced in Version 4.0.2; however, this feature worked only for new-format volumes (volumes that were created in new 4.0.2 clusters). Similarly, in Version 4.1, only new-format volumes that were created in 4.0.2 or 4.1 could be promoted to read-write.

However, starting in Version 5.0, you can upgrade old pre-4.0.2 volumes to the new format by using the maprcli volume upgradeformat command. After running this command on a specific volume, you can use the volume as a read-only or read-write volume by following standard procedures. New volumes that you create in Version 5.0 are created in the new format and are promotable automatically. You can continue to use old volumes as they are with no loss of functionality, but they will not be promotable.

The following sections provide information about how to use volume upgrades: