[ECE] Update steps of entire installation maintenance

[kunisen]

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• Before PR merge: deploy-manage/maintenance/ece/perform-ece-hosts-maintenance.md
• After PR merge: https://www.elastic.co/docs/deploy-manage/maintenance/ece/perform-ece-hosts-maintenance

Summary

Background

Our current doc about "shutting down all ECE hosts" is confusing and misleading:
https://www.elastic.co/docs/deploy-manage/maintenance/ece/perform-ece-hosts-maintenance#ece-perform-host-maintenance-delete-runner

• It says: By shutting down the host (less destructive) but it's actually shutting down ALL ECE hosts (per the description like Shut down all allocators:, etc).

• It says: Enable maintenance mode on the allocator., but given it's shutting down entire ECE and all hosts, it doesn't make sense to do this step, all service will be taken down.

• Also with some additional steps required in this scenario: We should stop routing request first, take snapshot, also we shouldn't recommend terminating deployments, etc.

Details are described in https://github.com/elastic/support-tech-lead/issues/1751.

Doc update detail

---

I had a sync from @R0ky and here's the note:

[1] Overview

Shuttind down all the runners (hosts) in an ECE deployment 
This method lets you temporarily shutt down all runners in an ECE deployment, e.g. for data center moves or planned power outages. It is offered as an non-guaranteed and less destructive alternative to fully rebuilding your ECE infrastructure. 

To shut down all the runners:

Disable traffic from load balancers.

Shut down all allocators

Shut down all non-director hosts.

Shut down directors.

[2] Steps

So this to stop:

• To shut down all the runners:
• Disable routing on all non system deployments
• Make sure all non system deployments are green
• Take snapshot on all deployments
• Disable traffic from load balancers.
• Shut down all allocators
• Shut down all non-director hosts.
• Shut down directors

To start:

• Start all directors.
• Verify that there is a healthy Zookeeper quorum (at least one zk_server_state leader, and zk_followers + zk_synced_followers should match the number of Zookeeper followers):
• Start all remaining hosts.
• Re-enable traffic from load balancers.
• Re-enable routing based on Deployment priority

Side notes

Snapshot

Chat with @AlexP-Elastic in this link

shutdown deployments: Do you agree that we should add make sure you have a good snapshot taken first,

++ (though let’s make sure we recommend not shutting them down at all - just mention if the customer has a good reason they need to, then they should)

system deployment

Chat with @AlexP-Elastic in this link

system deployments: Do you agree that we should add a note saying avoid shutting down system clusters

++

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Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

[github-actions]

Vale Linting Results

Summary: 7 suggestions found

💡 Suggestions (7)

File	Line	Rule	Message
deploy-manage/maintenance/ece/perform-ece-hosts-maintenance.md	43	Elastic.HeadingColons	Capitalize ': d'.
deploy-manage/maintenance/ece/perform-ece-hosts-maintenance.md	43	Elastic.WordChoice	Consider using 'deactivate, deselect, hide, turn off' instead of 'disable', unless the term is in the UI.
deploy-manage/maintenance/ece/perform-ece-hosts-maintenance.md	89	Elastic.HeadingColons	Capitalize ': d'.
deploy-manage/maintenance/ece/perform-ece-hosts-maintenance.md	89	Elastic.WordChoice	Consider using 'deactivate, deselect, hide, turn off' instead of 'disable', unless the term is in the UI.
deploy-manage/maintenance/ece/perform-ece-hosts-maintenance.md	188	Elastic.WordChoice	Consider using 'deactivate, deselect, hide, turn off' instead of 'Disable', unless the term is in the UI.
deploy-manage/maintenance/ece/perform-ece-hosts-maintenance.md	194	Elastic.WordChoice	Consider using 'stop, exit' instead of 'terminate', unless the term is in the UI.
deploy-manage/maintenance/ece/perform-ece-hosts-maintenance.md	194	Elastic.WordChoice	Consider using 'can, might' instead of 'may', unless the term is in the UI.

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[github-actions]

🔍 Preview links for changed docs

• deploy-manage/maintenance/ece/perform-ece-hosts-maintenance.md

[kunisen]

FWIW, got @R0ky's LGTM here