add(clickhouse): local on-disk cache for remote files

docs/products/clickhouse/concepts/clickhouse-tiered-storage.md

@@ -10,6 +10,8 @@ The tiered storage feature introduces a method of organizing and storing data in
 On top of this default data allocation mechanism, you can control the tier your
 data is stored in using custom data retention periods.
 
+## Tiered storage architecture
+
 The tiered storage in Aiven for ClickHouse® consists of the following two
 layers:
 
@@ -18,12 +20,22 @@ layers:
 - Object storage - the second tier: Affordable storage device with unlimited capability,
   better suited for historical and more rarely queried data, relatively slower
 
+Aiven for ClickHouse's tiered storage supports
+[local on-disk cache for remote files](/docs/products/clickhouse/howto/local-cache-tiered-storage),
+which is enabled by default. You can
+[disable the cache](/docs/products/clickhouse/howto/local-cache-tiered-storage#disable-the-cache)
+or
+[drop it](/docs/products/clickhouse/howto/local-cache-tiered-storage#free-up-space) to free
+up the space it occupies.
+
+## Supported cloud platforms
+
 On the Aiven tenant (in non-[BYOC](/docs/platform/concepts/byoc) environments), Aiven for
 ClickHouse tiered storage is supported on the following cloud platforms:
 
 - Microsoft Azure
 - Amazon Web Services (AWS)
-- Google Cloud Platform (GCP)
+- Google Cloud
 
 ## Why use it
 

docs/products/clickhouse/howto/local-cache-tiered-storage.md

@@ -0,0 +1,62 @@
+---
+title: Local on-disk cache for remote files in Aiven for ClickHouse®'s tiered storage
+sidebar_label: Local on-disk cache for remote files
+---
+
+Aiven for ClickHouse®'s tiered storage features local on-disk cache for remote files for improved query performance and reduced latency.
+
+To manage data, Aiven for ClickHouse's tiered storage uses local storage and remote storage.
+When remote storage is used, Aiven for ClickHouse leverages a local on-disk cache to avoid
+repeated remote fetches.
+
+## How it works
+
+When a query requires parts of a table stored in the remote tier, Aiven for ClickHouse
+fetches the required parts from the remote storage. The fetched parts are automatically
+stored in a local cache directory on the disk to avoid repeated downloads for subsequent
+queries. For future queries, Aiven for ClickHouse checks the local cache first:
+
+- If the data is found in the cache, it is read directly from the local disk.
+- If the data is not found in the cache, it is fetched from the remote storage and stored
+  in the local cache.
+
+Local on-disk cache for remote files is enabled by default for Aiven for ClickHouse's
+tiered storage. You can
+[disable the cache](/docs/products/clickhouse/howto/local-cache-tiered-storage#disable-the-cache)
+or
+[drop it](/docs/products/clickhouse/howto/local-cache-tiered-storage#free-up-space) to
+free up the space it occupies.
+
+## Prerequisites
+
+-   At least one Aiven for ClickHouse service using tiered storage
+-   Command line tool
+    ([ClickHouse client](/docs/products/clickhouse/howto/connect-with-clickhouse-cli))
+    installed
+
+## Disable the cache
+
+To disable the local cache for a query, set the `enable_filesystem_cache` setting for the
+query to `false`.
+You can achieve this by appending `SETTINGS enable_filesystem_cache = false` to the end of
+your query using an SQL client (for example, the
+[ClickHouse client](/docs/products/clickhouse/howto/connect-with-clickhouse-cli)):
+
+```sql
+SELECT 1
+SETTINGS enable_filesystem_cache = false;
+```
+
+## Free up space
+
+To drop the local cache and free up the used space, use the following cache command:
+
+```bash
+SYSTEM DROP FILESYSTEM CACHE 'remote_cache'
+```
+
+## Related pages
+
+-   [About tiered storage in Aiven for ClickHouse](/docs/products/clickhouse/concepts/clickhouse-tiered-storage)
+-   [Check data distribution between SSD and object storage](/docs/products/clickhouse/howto/check-data-tiered-storage)
+-   [Configure data retention thresholds for tiered storage](/docs/products/clickhouse/howto/configure-tiered-storage)

sidebars.ts

@@ -1301,6 +1301,7 @@ const sidebars: SidebarsConfig = {
                     'products/clickhouse/howto/configure-tiered-storage',
                     'products/clickhouse/howto/check-data-tiered-storage',
                     'products/clickhouse/howto/transfer-data-tiered-storage',
+                    'products/clickhouse/howto/local-cache-tiered-storage',
                   ],
                 },
               ],