docs: fix outdated Region size in multi-AZ deployment doc

[doc-claw-bot]

What is changed, added or deleted? (Required)

• Update multi-data-centers-in-one-city-deployment.md to use the current default Region size (256 MiB) instead of the outdated 96 MB.
• Keep the change scoped to the stale statement so the deployment guidance stays aligned with the current TiKV default used elsewhere in the docs.

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What is the related PR or file link(s)?

• This PR is translated from:
• Other reference link(s): docs: fix outdated Region size in multi-AZ deployment doc docs-cn#21964

AI agent involvement

• The changes in this PR were primarily made by an AI agent on behalf of the PR author.

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• Delete files
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• Might cause conflicts after applied to another branch

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[coderabbitai]

📝 Walkthrough

Walkthrough

The deployment documentation changes the documented default TiKV Region size from 96 MB to 256 MiB.

Changes

Region Size Documentation

Layer / File(s)	Summary
Update documented Region size multi-data-centers-in-one-city-deployment.md	The documented default TiKV Region size changes from 96 MB to 256 MiB.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~2 minutes

Change: Other

Merge Risk: 🔵 Low · up to 75a0a

The deployment guide may lead readers to treat 256 MiB as a fixed size for every Region. This is a bounded documentation issue and does not change runtime behavior.

Architecture Summary

Architecture risk: 🔵 Low · up to 75a0a

The change affects 1 system.

Changed systems: multi-data-centers-in-one-city-deployment.md

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — multi-data-centers-in-one-city-deployment.md (service) was modified; 1 changed file maps to changed impact.

Before / after behavior

• observed — Modified behavior in multi-data-centers-in-one-city-deployment.md: The documented default Region size changes from 96 MB to 256 MiB.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly identifies the documentation update and the outdated Region size it corrects.
Description check	✅ Passed	The description explains the change and its reason, identifies the affected versions, provides a related reference, and completes the applicable template sections.

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Actionable comments posted: 1

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ℹ️ Review info

⚙️ Run configuration

• Configuration used: Repository: pingcap/docs/.coderabbit.yaml
• Review profile: ASSERTIVE
• Plan: Advanced
• Run ID: f7ae5166-44a7-45d7-879e-e9c7baa451ed

📥 Commits

Reviewing files that changed from the base of the PR and between 6ba8576 and 75a0a4a.

📒 Files selected for processing (1)

• multi-data-centers-in-one-city-deployment.md

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[coderabbitai]

📐 Maintainability & Code Quality | 🟡 Minor | ⚡ Quick win

🔎 Supported by static analysis

🏁 Script executed:

git diff --unified=5 6ba85765e2f9e8d080a7f1789a3b46641a09d960 75a0a4aa8a4b955f6868ef1dadb80159d527cfd8 -- multi-data-centers-in-one-city-deployment.md
sed -n '1235,1252p' tikv-configuration-file.md
find .. -name AGENTS.md -o -name CONTRIBUTING.md

Repository: pingcap/docs

Length of output: 3253

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Describe 256 MiB as an estimate for newly split Regions.

The configuration reference describes region-split-size as an estimate for newly split Regions, not a fixed size for every Region. Update this sentence:

Suggested fix

-TiKV is a Multi-Raft system where data is divided into Regions and the size of each Region is 256 MiB by default. Three replicas of each Region form a Raft group. For a TiDB cluster of three replicas, because the number of Region replicas is independent of the TiKV instance numbers, three replicas of a Region are only scheduled to three TiKV instances. This means that even if the cluster is scaled out to have N TiKV instances, it is still a cluster of three replicas.
+TiKV is a Multi-Raft system where data is divided into Regions. The default estimated size for newly split Regions is 256 MiB. Three replicas of each Region form a Raft group. For a TiDB cluster of three replicas, because the number of Region replicas is independent of the TiKV instance numbers, three replicas of a Region are only scheduled to three TiKV instances. This means that even if the cluster is scaled out to have N TiKV instances, it is still a cluster of three replicas.

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

TiKV is a Multi-Raft system where data is divided into Regions and the size of each Region is 256 MiB by default. Three replicas of each Region form a Raft group. For a TiDB cluster of three replicas, because the number of Region replicas is independent of the TiKV instance numbers, three replicas of a Region are only scheduled to three TiKV instances. This means that even if the cluster is scaled out to have N TiKV instances, it is still a cluster of three replicas.

TiKV is a Multi-Raft system where data is divided into Regions. The default estimated size for newly split Regions is 256 MiB. Three replicas of each Region form a Raft group. For a TiDB cluster of three replicas, because the number of Region replicas is independent of the TiKV instance numbers, three replicas of a Region are only scheduled to three TiKV instances. This means that even if the cluster is scaled out to have N TiKV instances, it is still a cluster of three replicas.