doc: backup and restore documentation (#1688)

* doc: backup and restore documentation

* review and add MySQL

* Update backup-and-restore.md

---------

Co-authored-by: Anna Geller <anna.m.geller@gmail.com>
Co-authored-by: Will Russell <will@wrussell.co.uk>

content/docs/09.administrator-guide/backup-and-restore.md

@@ -0,0 +1,93 @@
+---
+title: Backup & Restore
+icon: /docs/icons/admin.svg
+---
+
+Backup Kestra.
+
+Kestra does not provide specific tools for backup and restore. However, Kestra uses a database and internal storage that can be backed up and restored.
+
+## Backup & Restore with the JDBC Backend
+
+With the JDBC backend, Kestra can be backed up and restored using the database's native backup tools. 
+
+### Backup & Restore for PostgreSQL
+
+First, stop Kestra to ensure the database is in a stable state. Although `pg_dump` allows you to back up a running PostgreSQL database, it's always better to perform backups offline when possible.
+
+Next, run the following command:
+
+```shell
+pg_dump -h localhost -p 5432 -U <username> -d <database> -F tar -f kestra.tar
+```
+
+To restore the backup to a new database, use `pg_restore`:
+
+```shell
+pg_restore -h localhost -p 5432 -U <username> -d <database> kestra.tar
+```
+
+Finally, restart Kestra.
+
+### Backup & Restore for MySQL
+
+First, stop Kestra to ensure the database is in a stable state. Although MySQL's `mysqldump` allows you to back up a running MySQL database, it's always better to perform backups offline when possible.
+
+Next, run the following command to back up the database:
+
+```shell
+mysqldump -h localhost -P 3306 -u <username> -p<password> <database> > kestra.sql
+```
+
+To restore the backup to a new database, use the following command:
+
+```shell
+mysql -h localhost -P 3306 -u <username> -p <password> <database> < kestra.sql
+```
+
+The `< kestra.sql` part tells MySQL to read and execute the SQL statements contained in the `kestra.sql` backup file as input.
+
+Finally, restart Kestra.
+
+---
+
+## Backup & Restore with the Elasticsearch and Kafka Backend
+
+With the Elasticsearch and Kafka backend, Kestra can be backed up and restored using Elasticsearch snapshots. Kafka will be reinitialized with the information from Elasticsearch.
+
+This guide assumes you have already configured a snapshot repository in Elasticsearch named `my_snapshot_repository`. Elasticsearch provides several [backup options](https://www.elastic.co/guide/en/elasticsearch/reference/current/snapshot-restore.html). We will leverage basic snapshot and restore operations using the Elasticsearch API.
+
+First, create an Elasticsearch snapshot named `kestra`:
+
+```
+PUT _snapshot/my_snapshot_repository/kestra?wait_for_completion=true
+```
+
+Next, delete all Kestra indices and recreate them using the snapshot:
+
+```
+POST _snapshot/my_snapshot_repository/kestra/_restore
+{
+  "indices": "kestra_*"
+}
+```
+
+If you need to start from a fresh Kafka instance, you can reindex Kafka from the data in Elasticsearch using the following Kestra command:
+
+```shell
+kestra sys restore-queue
+```
+
+Since some execution information is stored only in Kafka, not all pending executions may be restarted.
+
+Finally, restart Kestra.
+
+## Backup & Restore of Internal Storage
+
+Kestra's internal storage can be implemented using either a local filesystem or an object storage service.
+
+If you're using the local filesystem implementation, you can back up and restore the directory with standard filesystem backup tools.
+
+If you're using an object storage service provided by a cloud provider, you can replicate a bucket across multiple locations. Usually, this option is sufficient for disaster recovery. Alternatively, refer to your cloud provider's documentation for instructions on external bucket backup or replication to a different region.
+
+If you're running your own object storage (e.g., using MinIO from our Helm Chart), you can [leverage Restic](https://blog.min.io/back-up-restic-minio/) or set up a replication strategy that fits your needs.