[LU-18222] Implement quota aggregation limits by ID range

• Type: Bug
• Resolution: Unresolved
• Priority: Minor
• Labels: hard quota
• Severity: 3
• Epic Link: Project Quota aggregation group-range
• Assignee: Sergey Cheremencev
• Reporter: Andreas Dilger

Description

A number of sites have requested the ability to have hierarchical/nested project quotas in order to aggregate multiple project IDs for a tenant into a single aggregate limit, in order to restrict the total usage for multiple projects.

Rather than implement this at the level of the backing filesystem (which doesn't currently have space in the inode to store more IDs), one option would be for the MDS to add the quota usage from multiple project IDs into a single total, in a manner similar to OST pool quotas, and in general how the MDS is managing quota limits rather than quota accounting.

The MDS would sum the quota usage across all IDs in the aggregate, and then decide whether IDs would be granted new qunits when the OSTs have consumed their total space.

Some open questions include:

• what is a good name for this feature? "aggregate quota", "parent quota", "collective quota", other? "group quota" is already used.
• should this allow aggregating quotas from multiple/random disjoint project IDs? would it be enough to allow a range of IDs (e.g. 1000-1999 or 100000-199999) to be aggregated into single parent quota limit
• should an actual project ID (e.g. 1000 or 100000) be allocated as the placeholder for the "aggregate" quota accounting/limits? or should this grouping be "virtual" without an actual ID (which might cause confusion between the actual "p=1000" usage and the aggregate usage)
• should it be possible to aggregate a hierarchy of projects (e.g. 1000-1999 in one parent A, 3000-3999 into a second parent B, then add "A" and "B" into a third aggregate)? it may be that we can add this afterward on an as-needed basis, if it isn't easily done in the initial implementation

Issue Links

• is related to: LU-16857 OST object allocation should not select OSTs/pools where quota is exceeded
• is related to: LU-17166 add NRS TBF rule for projid
• is related to: LU-16771 add client statfs() cache for project quotas
• is related to: LU-18109 Nodemap UID/GID/PROJID idmap offsetting
• is related to: LU-11571 MDT pool