Use gitaly-backup for repository backups by default

Changelog: changed

config/feature_flags/development/gitaly_backup.yml

@@ -5,4 +5,4 @@ rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/333034
 milestone: '14.0'
 type: development
 group: group::gitaly
-default_enabled: false
+default_enabled: true

doc/raketasks/backup_restore.md

@@ -1472,3 +1472,47 @@ If this happens, examine the following:
 - Confirm there is sufficient disk space for the Gzip operation.
 - If NFS is being used, check if the mount option `timeout` is set. The
   default is `600`, and changing this to smaller values results in this error.
+
+### `gitaly-backup` for repository backup and restore **(FREE SELF)**
+
+> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/333034) in GitLab 14.2.
+> - [Deployed behind a feature flag](../user/feature_flags.md), enabled by default.
+> - Recommended for production use.
+> - For GitLab self-managed instances, GitLab administrators can opt to [disable it](#disable-or-enable-gitaly-backup).
+
+There can be
+[risks when disabling released features](../user/feature_flags.md#risks-when-disabling-released-features).
+Refer to this feature's version history for more details.
+
+`gitaly-backup` is used by the backup Rake task to create and restore repository backups from Gitaly.
+`gitaly-backup` replaces the previous backup method that directly calls RPCs on Gitaly from GitLab.
+
+The backup Rake task must be able to find this executable. It can be configured in Omnibus GitLab packages:
+
+1. Add the following to `/etc/gitlab/gitlab.rb`:
+
+   ```ruby
+   gitlab_rails['backup_gitaly_backup_path'] = '/path/to/gitaly-backup'
+   ```
+
+1. [Reconfigure GitLab](../administration/restart_gitlab.md#omnibus-gitlab-reconfigure)
+   for the changes to take effect
+
+#### Disable or enable `gitaly-backup`
+
+`gitaly-backup` is under development but ready for production use.
+It is deployed behind a feature flag that is **enabled by default**.
+[GitLab administrators with access to the GitLab Rails console](../administration/feature_flags.md)
+can opt to disable it.
+
+To disable it:
+
+```ruby
+Feature.disable(:gitaly_backup)
+```
+
+To enable it:
+
+```ruby
+Feature.enable(:gitaly_backup)
+```

lib/tasks/gitlab/backup.rake

@@ -297,7 +297,7 @@ namespace :gitlab do
     end
 
     def repository_backup_strategy
-      if Feature.enabled?(:gitaly_backup)
+      if Feature.enabled?(:gitaly_backup, default_enabled: :yaml)
         max_concurrency = ENV['GITLAB_BACKUP_MAX_CONCURRENCY'].presence
         max_storage_concurrency = ENV['GITLAB_BACKUP_MAX_STORAGE_CONCURRENCY'].presence
         Backup::GitalyBackup.new(progress, parallel: max_concurrency, parallel_storage: max_storage_concurrency)