Description of problem:
Tier is deprecated and is being removed from build (https://bugzilla.redhat.com/show_bug.cgi?id=1642807). The changes that are tightly coupled with DHT, glusterd and volume set has been planned to be removed separately.
This bug is to track the changes for removal.
Version-Release number of selected component (if applicable):
mainline and till 3.12
Steps to Reproduce:
Patch https://review.gluster.org/#/c/glusterfs/+/21331/ removes tier functionality from GlusterFS.
https://bugzilla.redhat.com/show_bug.cgi?id=1642807 is used as the tracking bug for this. Recommendation is to convert your tier volume to regular volume (either replicate, ec, or plain distribute) with "tier detach" command before upgrade, and use backend features like dm-cache etc to utilize the caching from backend to provide better performance and functionality.