Feature #11184

Updated by Tom Clegg over 3 years ago

As an Arvados system administrator, I want to take advantage of the cool/cold storage classes offered by cloud vendors.

This involves designating desired storage class(es) in some way (collection, all collections in a project, etc) as well as a way to migrate between storage classes.

[[Keep storage classes]]

h2. Overview

* Each keep volume offers one or more storage classes (the default is just the "default" class).
* Each collection has one or more desired storage classes (the default is just the "default" class).
* When writing, clients _may_ specify one or more required storage classes; if not, the required class is "default". A keepstore server will only write the data on a volume that offers _all_ of the required classes.
* Keep-balance moves data to volumes that have the desired attributes and updates collection records to reflect the storage classes currently satisfied by all blocks in the collection (much like replication level, these are not necessarily equal to the desired classes).

If overlapping collections (i.e., with common data blocks) request different storage classes, keep-balance will maintain multiple copies of the common blocks if necessary to satisfy all collections' requirements.

h2. Initial implementation

Simplifying restrictions in initial implementation (#12708): restrictions:
* No client side support.
* No keepstore support for writing data to a given storage class.
* API server configuration specifies the set of classes that can be requested (in addition to "default", which is always available).
* Keepstore configuration specifies the set of classes offered by each volume.