Cold Tier

Describes a cold tier.

On the data fabric cluster, every cold tier (referred to as remote target on the Data Fabric UI) has a bucket on a third-party cloud store where volume data is offloaded based on the policy configured by the administrator.

Volume data in 64KB data chunks is packed into 8MB sized objects and offloaded to the bucket on the tier and the corresponding volume metadata is stored in a visible tier-volume as HPE Ezmeral Data Fabric Database tables on the data fabric cluster.

During writes and reads, volume data is recalled to the data fabric cluster if necessary. Data written to the volume is periodically moved to the remote target, releasing the disk space on the filesystem. See Data Reads, Writes, and Recalls for more information.

Data stored on the data fabric cluster requires thrice the amount of disk space of the regular volume on premium hardware due to replication (default being 3). After offloading to the cloud, the space used by data (including data in the namespace container) in the volume on the data fabric cluster is freed and only the metadata of the volume in the namespace container is 3-way replicated on the data fabric cluster.

There is also a visible tier-volume on the data fabric cluster for storing the metadata associated with the volume. When you create a cold tier, the tier volume named mapr.internal.tier.<tierName> is by default created in the /var/mapr/tier path. A directory/folder for the volumes associated with the tier, identifiable by volumeid, is created under the path after the first offload of data from the volume to the tier.

You can create one tier per volume or create and associate multiple volumes with the same tier using the Data Fabric UI.