titan-configuration: remove the unrecommended steps of updating TiKV configuration (#21217) #21220
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Summary of Changes
Hello @ti-chi-bot, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
This pull request refines the documentation related to TiKV's Titan storage engine configuration, specifically focusing on the process of disabling Titan. The changes aim to provide safer and more accurate guidance to users, addressing potential system instability and performance degradation that could arise from previously recommended steps, especially for older TiDB versions. It also clarifies the default behavior and upgrade considerations for the rocksdb.titan.enabled configuration parameter.
Highlights
- Updated Titan Disabling Guidance: I've updated the documentation for disabling Titan in TiKV, providing more nuanced instructions and emphasizing that certain steps, like directly setting
rocksdb.titan.enabledtofalse, are no longer recommended for specific TiDB versions due to potential stability issues. - Removed Unrecommended Configuration Step: The explicit 'Step 4' instructing users to set
rocksdb.titan.enabled = falsein the configuration file has been removed from the Titan disabling guide, aligning with the new warnings about its usage. - Clarified
rocksdb.titan.enabledDefault Behavior: The documentation for therocksdb.titan.enabledconfiguration item has been updated to reflect its default value changing fromfalsetotruestarting from TiDB v7.6.0, along with important notes on upgrade behavior and performance implications. - Added Critical Warnings: New warnings have been added to both the Titan configuration guide and the
tikv-configuration-filereference, advising against settingrocksdb.titan.enabledtofalsefor TiDB versions earlier than v8.5.0 to prevent TiKV crashes.
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| <<<<<<< HEAD | ||
| To fully disable Titan for all existing and future data, you can follow these steps: | ||
| ======= | ||
| To disable Titan for all existing and future data, you can take the following steps. Note that you can skip Step 2 because it greatly affects online traffic performance. In fact even without Step 2, the data compaction consumes extra I/O and CPU resources when it moves data from Titan to RocksDB, and performance will degrade (sometimes as much as 50%) when TiKV I/O or CPU resources are limited. | ||
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| > **Warning:** | ||
| > | ||
| > When disabling Titan for TiDB versions earlier than v8.5.0, it is not recommended to modify the TiKV configuration item [`rocksdb.titan.enabled`](/tikv-configuration-file.md#enabled) to `false`, as this might cause TiKV to crash. Following Step 1 is sufficient to disable Titan. | ||
| >>>>>>> 445dea0c18 (titan-configuration: remove the unrecommended steps of updating TiKV configuration (#21217)) |
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Merge conflict markers detected. Please resolve the conflict by choosing the appropriate content and removing the markers.
| <<<<<<< HEAD | |
| To fully disable Titan for all existing and future data, you can follow these steps: | |
| ======= | |
| To disable Titan for all existing and future data, you can take the following steps. Note that you can skip Step 2 because it greatly affects online traffic performance. In fact even without Step 2, the data compaction consumes extra I/O and CPU resources when it moves data from Titan to RocksDB, and performance will degrade (sometimes as much as 50%) when TiKV I/O or CPU resources are limited. | |
| > **Warning:** | |
| > | |
| > When disabling Titan for TiDB versions earlier than v8.5.0, it is not recommended to modify the TiKV configuration item [`rocksdb.titan.enabled`](/tikv-configuration-file.md#enabled) to `false`, as this might cause TiKV to crash. Following Step 1 is sufficient to disable Titan. | |
| >>>>>>> 445dea0c18 (titan-configuration: remove the unrecommended steps of updating TiKV configuration (#21217)) | |
| To disable Titan for all existing and future data, you can take the following steps. Note that you can skip Step 2 because it greatly affects online performance. Even without Step 2, data compaction consumes extra I/O and CPU resources when moving data from Titan to RocksDB, and performance will degrade (sometimes as much as 50%) when TiKV I/O or CPU resources are limited. | |
| > **Warning:** | |
| > | |
| > When disabling Titan for TiDB versions earlier than v8.5.0, it is not recommended to modify the TiKV configuration item [`rocksdb.titan.enabled`](/tikv-configuration-file.md#enabled) to `false`, as this might cause TiKV to crash. Following Step 1 is sufficient to disable Titan. |
| <<<<<<< HEAD | ||
| 4. Update the configuration of these TiKV nodes to disable Titan. | ||
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| ```toml | ||
| [rocksdb.titan] | ||
| enabled = false | ||
| ``` | ||
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||
| ======= | ||
| >>>>>>> 445dea0c18 (titan-configuration: remove the unrecommended steps of updating TiKV configuration (#21217)) |
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Merge conflict markers detected. Please resolve the conflict by choosing the appropriate content and removing the markers.
tikv-configuration-file.md
Outdated
| <<<<<<< HEAD | ||
| + Enables or disables Titan | ||
| + Default value: `false` | ||
| ======= | ||
| > **Warning** | ||
| > | ||
| > When disabling Titan for TiDB versions earlier than v8.5.0, it is not recommended to modify this configuration item to `false`, as this might cause TiKV to crash. To disable Titan, refer to the steps in [Disable Titan](/storage-engine/titan-configuration.md#disable-titan). | ||
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| > **Note:** | ||
| > | ||
| > - To enhance the performance of wide table and JSON data writing and point query, starting from TiDB v7.6.0, the default value changes from `false` to `true`, which means that Titan is enabled by default. | ||
| > - Existing clusters upgraded to v7.6.0 or later versions retain the original configuration, which means that if Titan is not explicitly enabled, it still uses RocksDB. | ||
| > - If the cluster has enabled Titan before upgrading to TiDB v7.6.0 or later versions, Titan will be retained after the upgrade, and the [`min-blob-size`](/tikv-configuration-file.md#min-blob-size) configuration before the upgrade will be retained. If you do not explicitly configure the value before the upgrade, the default value of the previous version `1KiB` will be retained to ensure the stability of the cluster configuration after the upgrade. | ||
|
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| + Enables or disables Titan. | ||
| + Default value: `true` | ||
| >>>>>>> 445dea0c18 (titan-configuration: remove the unrecommended steps of updating TiKV configuration (#21217)) |
There was a problem hiding this comment.
Merge conflict markers detected. Please resolve the conflict by choosing the appropriate content and removing the markers.
| <<<<<<< HEAD | |
| + Enables or disables Titan | |
| + Default value: `false` | |
| ======= | |
| > **Warning** | |
| > | |
| > When disabling Titan for TiDB versions earlier than v8.5.0, it is not recommended to modify this configuration item to `false`, as this might cause TiKV to crash. To disable Titan, refer to the steps in [Disable Titan](/storage-engine/titan-configuration.md#disable-titan). | |
| > **Note:** | |
| > | |
| > - To enhance the performance of wide table and JSON data writing and point query, starting from TiDB v7.6.0, the default value changes from `false` to `true`, which means that Titan is enabled by default. | |
| > - Existing clusters upgraded to v7.6.0 or later versions retain the original configuration, which means that if Titan is not explicitly enabled, it still uses RocksDB. | |
| > - If the cluster has enabled Titan before upgrading to TiDB v7.6.0 or later versions, Titan will be retained after the upgrade, and the [`min-blob-size`](/tikv-configuration-file.md#min-blob-size) configuration before the upgrade will be retained. If you do not explicitly configure the value before the upgrade, the default value of the previous version `1KiB` will be retained to ensure the stability of the cluster configuration after the upgrade. | |
| + Enables or disables Titan. | |
| + Default value: `true` | |
| >>>>>>> 445dea0c18 (titan-configuration: remove the unrecommended steps of updating TiKV configuration (#21217)) | |
| > **Warning:** | |
| > | |
| > When disabling Titan for TiDB versions earlier than v8.5.0, it is not recommended to modify this configuration item to `false`, as this might cause TiKV to crash. To disable Titan, refer to the steps in [Disable Titan](/storage-engine/titan-configuration.md#disable-titan). | |
| > **Note:** | |
| > | |
| > - To enhance the performance of wide table and JSON data writing and point query, starting from TiDB v7.6.0, the default value changes from `false` to `true`, which means that Titan is enabled by default. | |
| > - Existing clusters upgraded to v7.6.0 or later versions retain the original configuration, which means that if Titan is not explicitly enabled, it still uses RocksDB. | |
| > - If the cluster has enabled Titan before upgrading to TiDB v7.6.0 or later versions, Titan will be retained after the upgrade, and the [`min-blob-size`](/tikv-configuration-file.md#min-blob-size) configuration before the upgrade will be retained. If you do not explicitly configure the value before the upgrade, the default value of the previous version `1KiB` will be retained to ensure the stability of the cluster configuration after the upgrade. | |
| + Enables or disables Titan. | |
| + Default value: `true` |
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[APPROVALNOTIFIER] This PR is APPROVED This pull-request has been approved by: qiancai The full list of commands accepted by this bot can be found here. The pull request process is described here
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This is an automated cherry-pick of #21217
First-time contributors' checklist
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This PR updates release-8.1 docs according to pingcap/docs-cn#20304.
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