Data Tier correlation for searchable_snapshot mount location

[stefnestor]

Per @andreidan wisdom:

searchable snapshots are mounted directly on the corresponding data tiers (namely, fully mounted indices on the hot, cold or frozen tiers (depending on the ILM phase where the searchable_action is defined) while the partially mounted indices are mounted on the frozen tier).

This points out the prerequisite of the corresponding data tier for the searchable_snapshot phase.

[elasticmachine]

Pinging @elastic/es-docs (Team:Docs)

[elasticmachine]

Pinging @elastic/es-distributed (Team:Distributed)

[elasticmachine]

Pinging @elastic/es-core-features (Team:Core/Features)

[jrodewig]

Thanks for this clarification @stefnestor.

In addition to your change, I added a sentence to make it clearer that the action requires data tiers. I also moved the last sentence to the first paragraph.

This LGTM, but I'll wait on @andreidan's review before merging.

[mark-vieira]

@elasticmachine retest this please

[mark-vieira]

@elasticmachine retest this please

[andreidan]

I've left a minor suggestion, thanks for working on this Stef!

[andreidan]

Could we expand this a bit and say something like:

The `searchable_snapshot` action requires a system that uses <<data-tiers,data tiers>> 
as it will mount the index directly on the corresponding tier using the
 <<tier-preference-allocation-filter, `index.routing.allocation.include._tier_preference`>> setting.

Maybe @jrodewig has a better suggestion here? (I don't particularly like "a system that uses ..." but not sure how else to phrase this).

[jrodewig]

Thanks @andreidan. I pushed some changes to incorporate the index.routing.allocation.include._tier_preference setting content.

[andreidan]

Thanks James

[jrodewig]

@elasticmachine run elasticsearch-ci/docs

[stefnestor]

@jrodewig can we also back port this applicable info to 7.12, 7.11, & 7.10? I know we back ported to 7.x (thank you!), but if we still back port to the other version it'd help as well. 🙏🏼

[jrodewig]

Hi @stefnestor. Thanks for reaching out.

Per our backport guidelines, we typically don't backport doc changes to out-of-maintenance versions. However, I'll work on getting these in as it seems to be a problem point.