Keep storage tiers¶

Typically, an Arvados cluster has access to multiple storage devices with different cost/performance trade-offs.

• Local SSD
• Local HDD
• Object storage service provided by cloud vendor
• Slower or less reliable object storage service provided by same cloud vendor

Users should be able to specify a minimum storage tier for each collection. Arvados should ensure that every data block referenced by a collection is stored at the specified tier or better.

The cluster administrator should be able to specify a default tier, and assign a tier number to each storage device.

It should be possible to configure multiple storage devices at the same tier: for example, this allows blocks to be distributed more or less uniformly across multiple cloud storage buckets for performance reasons.