chore(v1): Cautions, risks, and mitigations for using truncate-shards with future data

- Closes influxdata/DAR/issues/534
- Contact Support for assistance
- Add risks and technical details to truncate-shard command
- Add cautions to rebalance guide
- Add planning guidance for future data in schema_and_data_layout

content/enterprise_influxdb/v1/administration/manage/clusters/rebalance.md

@@ -40,11 +40,20 @@ cluster, and they use the
 [`influxd-ctl` tool](/enterprise_influxdb/v1/tools/influxd-ctl/) available on
 all meta nodes.
 
-{{% warn %}}
-Before you begin, stop writing historical data to InfluxDB.
-Historical data have timestamps that occur at anytime in the past.
-Performing a rebalance while writing historical data can lead to data loss.
-{{% /warn %}}
+> [!Warning]
+> #### Stop writing data before rebalancing
+>
+> Before you begin, stop writing historical data to InfluxDB.
+> Historical data have timestamps that occur at anytime in the past.
+> Performing a rebalance while writing historical data can lead to data loss.
+
+> [!Caution]
+> #### Risks of rebalancing with future data
+>
+> Truncating shards that contain data with future timestamps (such as forecast or prediction data)
+> can lead to overlapping shards and data duplication.
+> For more information, see [`truncate-shards` and future data](/enterprise_influxdb/v1/tools/influxd-ctl/truncate-shards/#understand-the-risks-with-future-data)
+> or [contact InfluxData support](https://support.influxdata.com).
 
 ## Rebalance Procedure 1: Rebalance a cluster to create space
 
@@ -67,6 +76,14 @@ Hot shards are shards that are currently receiving writes.
 Performing any action on a hot shard can lead to data inconsistency within the
 cluster which requires manual intervention from the user.
 
+> [!Caution]
+> #### Risks of rebalancing with future data
+>
+> Truncating shards that contain data with future timestamps (such as forecast or prediction data)
+> can lead to overlapping shards and data duplication.
+> For more information, see [`truncate-shards` and future data](/enterprise_influxdb/v1/tools/influxd-ctl/truncate-shards/#understand-the-risks-with-future-data)
+> or [contact InfluxData support](https://support.influxdata.com).
+
 To prevent data inconsistency, truncate hot shards before moving any shards
 across data nodes.
 The command below creates a new hot shard which is automatically distributed
@@ -298,6 +315,14 @@ Hot shards are shards that are currently receiving writes.
 Performing any action on a hot shard can lead to data inconsistency within the
 cluster which requires manual intervention from the user.
 
+> [!Caution]
+> #### Risks of rebalancing with future data
+>
+> Truncating shards that contain data with future timestamps (such as forecast or prediction data)
+> can lead to overlapping shards and data duplication.
+> For more information, see [`truncate-shards` and future data](/enterprise_influxdb/v1/tools/influxd-ctl/truncate-shards/#understand-the-risks-with-future-data)
+> or [contact InfluxData support](https://support.influxdata.com).
+
 To prevent data inconsistency, truncate hot shards before copying any shards
 to the new data node.
 The command below creates a new hot shard which is automatically distributed

content/enterprise_influxdb/v1/concepts/schema_and_data_layout.md

@@ -16,6 +16,7 @@ We recommend the following design guidelines for most use cases:
   - [Where to store data (tag or field)](#where-to-store-data-tag-or-field)
   - [Avoid too many series](#avoid-too-many-series)
   - [Use recommended naming conventions](#use-recommended-naming-conventions)
+  - [Writing data with future timestamps](#writing-data-with-future-timestamps)
   - [Shard Group Duration Management](#shard-group-duration-management)
 
 ## Where to store data (tag or field)
@@ -209,6 +210,38 @@ from(bucket:"<database>/<retention_policy>")
 > SELECT mean("temp") FROM "weather_sensor" WHERE region = 'north'
 ```
 
+## Writing data with future timestamps
+
+When designing schemas for applications that write data with future timestamps--such as forecast data from machine learning models, predictions, or scheduled events--consider the following implications for InfluxDB Enterprise v1 cluster operations and data integrity.
+
+### Understanding future data behavior
+
+InfluxDB Enterprise v1 creates shards based on time ranges.
+When you write data with future timestamps, InfluxDB creates shards that cover future time periods.
+
+> [!Caution]
+> #### Risks of rebalancing with future data
+>
+> Truncating shards that contain data with future timestamps (such as forecast or prediction data)
+> can lead to overlapping shards and data duplication.
+> For more information, see [`truncate-shards` and future data](/enterprise_influxdb/v1/tools/influxd-ctl/truncate-shards/#understand-the-risks-with-future-data)
+> or [contact InfluxData support](https://support.influxdata.com).
+
+### Use separate databases for future data
+
+When planning for data that contains future timestamps, consider isolating it in dedicated databases to:
+
+- Minimize impact on real-time data operations
+- Allow targeted maintenance operations on current vs. future data
+- Simplify backup and recovery strategies for different data types
+
+```sql
+# Example: Separate databases for different data types
+CREATE DATABASE "realtime_metrics"
+CREATE DATABASE "ml_forecasts"
+CREATE DATABASE "scheduled_predictions"
+```
+
 ## Shard group duration management
 
 ### Shard group duration overview

content/enterprise_influxdb/v1/tools/influxd-ctl/truncate-shards.md

@@ -17,6 +17,14 @@ The `influxd-ctl truncate-shards` command truncates all shards that are currentl
 being written to (also known as "hot" shards) and creates new shards to write
 new data to.
 
+> [!Caution]
+> #### Overlapping shards with forecast and future data
+>
+> Running `truncate-shards` on shards containing future timestamps can create 
+> overlapping shards with duplicate data points.
+>
+> [Understand the risks with future data](#understand-the-risks-with-future-data).
+
 ## Usage
 
 ```sh
@@ -40,3 +48,34 @@ _Also see [`influxd-ctl` global flags](/enterprise_influxdb/v1/tools/influxd-ctl
 ```bash
 influxd-ctl truncate-shards -delay 3m
 ```
+
+## Understand the risks with future data
+
+> [!Important]
+> If you need to rebalance shards that contain future data, contact [InfluxData support](https://www.influxdata.com/contact/) for assistance.
+
+When you write data points with timestamps in the future (for example, forecast data from machine learning models),
+the `truncate-shards` command behaves differently and can cause data duplication issues.
+
+### How truncate-shards normally works
+
+For shards containing current data:
+1. The command creates an artificial stop point in the shard at the truncation timestamp
+2. Creates a new shard starting from the truncation point
+3. Example: A one-week shard (Sunday to Saturday) becomes:
+   - Shard A: Sunday to truncation point (Wednesday 2pm)
+   - Shard B: Truncation point (Wednesday 2pm) to Saturday
+   
+This works correctly because the meta nodes understand the boundaries and route queries appropriately.
+
+### The problem with future data
+
+For shards containing future timestamps:
+1. The truncation doesn't cleanly split the shard at a point in time
+2. Instead, it creates overlapping shards that cover the same time period
+3. Example: If you're writing September forecast data in August:
+   - Original shard: September 1-7
+   - After truncation: 
+     - Shard A: September 1-7 (with data up to truncation)
+     - Shard B: September 1-7 (for new data after truncation)
+   - **Result**: Duplicate data points for the same timestamps