Clarify backup block device storage requirements (#56553)

Co-authored-by: Vanessa <[email protected]>

Author: ThatStoney

content/admin/backing-up-and-restoring-your-instance/backup-service-for-github-enterprise-server/configuring-the-backup-service.md

@@ -21,7 +21,7 @@ Before configuring the backup service, ensure you have:
 
 To ensure reliable and performant backups, your storage must meet the following requirements:
 
-* **Capacity:** Allocate at least five times the amount of storage used by your primary {% data variables.product.github %} appliance disk. This accounts for historical snapshots and future growth.
+* **Capacity:** Allocate at least five times the amount of storage used by your primary {% data variables.product.github %} appliance data disk. This accounts for historical snapshots and future growth.
 * **Filesystem support:** The backup service uses hard links for efficient storage, and your {% data variables.product.github %} instance uses symbolic links. The backup target must support both symbolic and hard links, and it must use a case-sensitive filesystem to prevent conflicts.
 
   You can test whether your filesystem supports hardlinking symbolic links by running: