Amanda Staging Area is also referred to as Holding disks in Amanda documentation. Zmanda Management Console (ZMC) refers to it as Staging Area.
Zmanda Management Console allows configuration of one directory in the Amanda server as staging area for backups.
Staging area should be in direct attached or SAN attached storage connected to the Amanda server. Use of NFS or CIFS storage for staging area is not recommended because backup will take extra network hops.
Amanda uses Staging area for two reasons:
To increase parallelism between data transfer between Amanda server and client. This reduces the backup window and reduces the impact on the client (production servers).
Fault tolerance: In case of media failure (such as correct tapes not loaded), the backup images are stored in the Staging area.
The staging area location used during backup is not the same as Restore Temporary Directory in the Zmanda Management Console.
Backup images in Staging Area
Backup images in the staging area are part of Amanda catalog and will be considered for recovery.
Backup images in the staging area are automatically moved to secondary media (flushed) during the next backup run. This is controlled by Auto Flush parameter in ZMC Backup| Staging page. The backup images are flushed in FIFO order.
Amanda provides commands to list the backup images in the staging area and delete them if they are no longer required.
Staging area can be changed from ZMC Backup| Staging page as long as backup images are not in the staging area. If there are backup images in the original staging area, they can be no longer moved to media. The new Staging area directory must be owned by amandabackup user and must be readable and writable only by owner. This check is performed to maintain the security of the backup images.
Staging area cannot be disabled and multiple staging areas for a backup set cannot be configured using Zmanda Management Console. It can be done by manual configuration changes.
Staging Area Sizing
Staging area is optional and Amanda can take advantage of the space available in staging area to the maximum during the backup run.
Recommended Staging area capacity should be at least one full backup (after compression) image size for the backup set.
The Staging area size can be changed by increasing size in the ZMC Backup| Staging page or adding more staging area locations (requires configuration change) or using adding disks to logical volume or to a storage LUN and extending the file system.