Gargi-jais11 commented on code in PR #436: URL: https://github.com/apache/ozone-site/pull/436#discussion_r3273118763
########## docs/05-administrator-guide/02-configuration/04-performance/11-storage-capacity-planning.md: ########## @@ -0,0 +1,142 @@ +--- +sidebar_label: Storage Capacity Planning +--- + +# Storage Capacity Planning + +In Apache Ozone, managing disk capacity is critical for maintaining high availability. Ozone uses a multi-layered approach to ensure that Datanodes do not run out of physical space, which could lead to data corruption or service hangs. + +For background on Datanode volumes and related settings, see [Datanodes](../../../core-concepts/architecture/datanodes). Full property descriptions are in the [configuration appendix](../appendix). + +## When is a Disk Considered "Full"? + +A disk (or "Volume" in Ozone terminology) is considered **Full** for new data allocations and replication targets when the available physical space falls below a specific threshold. + +This threshold is the sum of two "Reserved Space" configurations plus a safety buffer for the operation itself: + +`Failure Threshold = (Volume Min Free Space) + (DU Reserved Space) + (Operation Buffer)` + +If a volume's free space is less than this threshold, SCM will stop selecting this volume for new containers or as a destination for re-replication (including decommission and maintenance moves). + +## Reserved Space Concepts + +Ozone provides two types of reserved space to protect the system: + +### 1. Volume Min Free Space + +This is a safety margin managed by the Datanode to prevent the disk from ever reaching 100% capacity. It is the most important setting for capacity planning. + +- **Purpose**: Protects the Datanode from OS-level disk-full errors. +- **Configuration**: + - `hdds.datanode.volume.min.free.space`: A fixed value (e.g., `20GB`). Review Comment: @jojochuang Should we also mention about volume min free space hard limit? **- Soft limit (min.free.space.percent, default 2%):** used for what is reported to SCM in heartbeats as freeSpaceToSpare. This governs SCM placement decisions. **- Hard limit (min.free.space.hard.limit.percent, default 1.5%):** used for local write rejection on the Datanode. ########## docs/05-administrator-guide/02-configuration/04-performance/11-storage-capacity-planning.md: ########## @@ -0,0 +1,142 @@ +--- +sidebar_label: Storage Capacity Planning +--- + +# Storage Capacity Planning + +In Apache Ozone, managing disk capacity is critical for maintaining high availability. Ozone uses a multi-layered approach to ensure that Datanodes do not run out of physical space, which could lead to data corruption or service hangs. + +For background on Datanode volumes and related settings, see [Datanodes](../../../core-concepts/architecture/datanodes). Full property descriptions are in the [configuration appendix](../appendix). + +## When is a Disk Considered "Full"? + +A disk (or "Volume" in Ozone terminology) is considered **Full** for new data allocations and replication targets when the available physical space falls below a specific threshold. + +This threshold is the sum of two "Reserved Space" configurations plus a safety buffer for the operation itself: + +`Failure Threshold = (Volume Min Free Space) + (DU Reserved Space) + (Operation Buffer)` + +If a volume's free space is less than this threshold, SCM will stop selecting this volume for new containers or as a destination for re-replication (including decommission and maintenance moves). + +## Reserved Space Concepts + +Ozone provides two types of reserved space to protect the system: + +### 1. Volume Min Free Space + +This is a safety margin managed by the Datanode to prevent the disk from ever reaching 100% capacity. It is the most important setting for capacity planning. + +- **Purpose**: Protects the Datanode from OS-level disk-full errors. +- **Configuration**: + - `hdds.datanode.volume.min.free.space`: A fixed value (e.g., `20GB`). + - `hdds.datanode.volume.min.free.space.percent`: A percentage of the volume capacity (e.g., `0.02` for 2%). +- **Logic**: Ozone uses the **maximum** of the fixed value and the percentage. + +### 2. DU Reserved Space + +This reserves space for non-Ozone files on the same disk (e.g., OS logs, system tools, or other services). + +- **Purpose**: Prevents Ozone from consuming space that is intended for other uses on the host. +- **Configuration**: + - `hdds.datanode.dir.du.reserved`: Fixed bytes per volume (e.g., `/data1:500MB`). + - `hdds.datanode.dir.du.reserved.percent`: Percentage per volume (default is `0.0001` or 0.01%). + +### 3. Operation Buffer (2x Container Size) + +When Ozone replicates a container (e.g., during decommissioning), it requires space to hold the incoming data in a temporary directory before importing it. + +- **Requirement**: Ozone requires free space equal to **2x the Container Size**. +- **Example**: For a default 5 GB container, this is **10 GB**. + +## Configuration Parameters + +| Property | Default | Description | +| :--- | :--- | :--- | +| `hdds.datanode.volume.min.free.space` | `20GB` | Fixed minimum free space per volume. | +| `hdds.datanode.volume.min.free.space.percent` | `0.02` (2%) | Percentage-based minimum free space. | +| `hdds.datanode.dir.du.reserved` | (unset) | Fixed bytes reserved for non-Ozone use. | +| `ozone.scm.container.size` | `5GB` | The target size for containers. | +| `hdds.datanode.storage.utilization.critical.threshold` | `0.95` (95%) | Threshold at which SCM logs a "Critical" space warning. | + +## Inspecting Storage Usage + +Administrators can inspect the actual and "SCM-usable" space using the Ozone CLI or the Recon Web UI. + +### 1. Recon Web UI + +The [Recon cluster capacity guide](../../operations/observability/recon/recon-capacity-distribution) describes how to monitor cluster-wide storage: + +- **Dashboards**: View aggregated capacity, used space, and remaining space for the entire cluster. +- **Datanodes Page**: Sort Datanodes by utilization to quickly identify nodes that are approaching their "Full" threshold. + +### 2. Node Usage Summary (CLI) + +To see a high-level view of how much space is used across the cluster: + +```bash +ozone admin datanode usageinfo +``` + +This command shows the capacity, SCM used, and remaining space for each Datanode. + +### 3. Detailed Volume Info + +To see the status of individual disks on a specific Datanode: + +```bash +ozone admin datanode usageinfo --uuid <datanode-uuid> Review Comment: uuid is deprecated. ```suggestion ozone admin datanode usageinfo --node-id <datanode-node-id> ``` -- This is an automated message from the Apache Git Service. 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