Allow VO override for repack

Problem to solve

After several iterations over 2 specific CTA operations workflows:

• tape repack
• tape verification

We converged toward similar constraints and mechanisms:

• operators will trigger each of these by providing a specific mountpolicy
• some standard queue settings must be overridden at submission time

For example for REPACK, cta.repack.repack_buffer_url overrides the destination of retrieve requests.

Regarding the drive allocation and accounting, transfer volume allocation and accounting CTA has only 1 mechanism: VO.

Indeed: VOs allow to constrain maxreaddrives for READ and WRITE in CTA and it is used to account data movements to a specific experiment.

On top of that with the new schema 10, VO is elastically bound to a specific diskinstance.

For all these reasons we decided together that REPACK require its own VO but we currently are lacking a mechanism to override the VO at submission time.

Proposal

We have 2 possibilities:

• allow mountpolicy to override the VO
• add another override mechanism for VO in the frontend configuration file

For now overriding VO is compulsory for REPACK as operators need some controls independent of the experiment traffic to control how repack should be progressing.

Do we need this for VERIFICATION as well or not?