[HDDS-8410] Implement storage policies

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Assignee: Unassigned
• Reporter: Maksim Myskov
• Created: 12/Apr/23 13:59
• Updated: 13/Apr/23 22:42

Description

In order to optimize read performance, it is required to implement HDFS-like storage policies: HOT, WARM, COLD.

HOT:  all container’s replicas are stored on fast storage

WARM: one container replica is stored on fast storage, others are stored on regular storage

COLD: all container’s replicas are stored on slow storage

 

Use case example 1:

There is a cluster of K datanodes. Each datanode has N regular disks and M fast disks.

 

Use case example 2:

There is a cluster of N regular datanodes and M fast datanodes. Regular datanodes have regular (HDD) disks and fast datanodes have fast (SSD) disks.

 

Requirements:

• If a container’s heat state (hot-warm-cold) changes, container can be moved to a different disk on the same node or to a different node, depending on the cluster configuration.
• container’s heat is automatically calculated based on data request statistics.
• A file/directory’s heat state can be set manually. Example: if one set “key1/subkey/*” to be HOT data, all chunks related to this prefix must be considered HOT despite heatmap.

Open questions:

• How to calculate data heat map? A possible solution is that statistics are collected by datanodes and then sent to SCM in reports. SCM analyses these reports to build an actual data heat map.

Issue Links

• Is contained by: HDDS-7711 Enable support for heterogeneous storages in Ozone