Backup How

After you have defined what, where and when for the backup set, you can use the Backup How page to define some of the key internal parameters that control how the backup set will run after it has been activated. In most situations, the default values set for these parameters will work well for most backup sets and therefore need not be changed.

Advanced users intending to modify the default values should study the logs of a few past backup runs in light of the discussion that follows.

Backup How Page Overview

Overview Backup How

Backup How is the last stage in backup set configuration.

Backup How Page Main Functionality

The Backup How page lets you set rules for how backup runs will be performed.

  • The left panel specifies backup timeouts and notification parameters.
  • The right panel specifies backup parameters that impact the backup window.

Warning: Do not simultaneously modify these parameters directly in the Amanda configuration file while you are editing them with ZMC. If you want to edit the Amanda configuration file directly, first log out the ZMC session.

Time Outs & Notification Parameters

Time Outs and Notification Parameters

The left panel of the Backup How page contains the timeout and notifications parameters.

Mail Address
Sets the e-mail address of the Amanda backup administrator. Though this is an optional parameter, it is important to set the Notification parameter to the email address(es) of the Amanda administrator. Amanda backup run notifications will be sent to the email address. The email address can be different from the email address set in the Admin page for a particular user. ZMC also provides content of the notification in the Report Summary page for the backup set. To email reports and notifications to more than one user, set up a group email alias on your mail server and enter that address here.
The Mail User Agent (MUA) such as Mail should be configured on the Amanda server before any email can be sent. ZMC does not install or configure the MUA.
Backup Estimate Time Out
Limits the amount of time the ZMC will spend on the first phase (Planning phase) of the backup process. The Amanda backup process first estimates backup size for each DLE configured in the backup set. The backup size estimation for all DLEs in the backup set is done in parallel.
Specify a time out (in Seconds) by which each Amanda client has to respond with a backup size estimate.
If the time out occurs for a particular DLE, that DLE will not be backed up during the backup run. Amanda will perform a full backup for the DLE in the next backup run.
The time out specified should take into account factors such as clients with limited network bandwidth, limited CPU, multiple DLEs on one host, and clients with large amounts of data to be backed up.
Some idea of the time being taken to perform size estimates can be had from the Monitor page where details of the current backup run are displayed. A much better idea can be had from the Report Time line page where DLE-wise details are displayed.
If a DLE has timed out, it will be displayed in red. Other DLEs are displayed in green.
Verification Time Out
ZMC lets you verify configuration of the Amanda clients on the Verify page. Verification Time out controls the time (in Seconds) that the verification tool waits for the client to respond to verification requests.
The time out may be adjusted for clients with limited network bandwidth.
If the time out expires, the verification of the client fails.
This time out has no impact on the backup process. If the client is properly set up, it will be backed up.
The time out applies to all clients in the backup set.
Data Time Out
Limits the time (in Seconds) that the Amanda server will wait (during the backup execution phase) for a client to begin to respond to a backup request.
If data time out occurs for a client, the backup of all directories for the client is not done in the backup run. The directories on the client will be backed up in the next backup run.
The time out may be adjusted for clients with limited network bandwidth.
The time out applies to all clients in the backup set.

Performance Parameters

Performance Parameters are grouped in the Right Hand panel (No. 2) labeled as such.

Media Utilization
Staging area holding disks are written in parallel. By the time the first completed DLE backup has been written to the media, many more DLEs backups may also be ready to be moved. This parameter sets the algorithm that determines the order in which the completed backup images are moved from holding disk to the backup media.
Only completed backup images on the holding disk are considered for moving; the ordering of the images can help in better utilization of backup media.
Options are:
  • First: (Default value) First in - first out.
  • Firstfit: The first backup image that will fit on the current media volume.
  • Largest: The largest backup image first.
  • Largestfit: The largest backup image that will fit on the current media volume.
  • Smallest: The smallest backup image first.
  • Last: Last in - first out.
Parallel Backups
Sets the number of parallel data backups that are performed from the Amanda clients to the holding disk in a backup run. The default value is 10. How many parallel backups happen to the staging area/holding disk depends on
  • CPU and Write speed on the Amanda server
  • Network configuration between the Amanda server and Amanda client
Backup Order
Whenever two or more parallel streams need simultaneous access to the same media volume, there is a potential conflict: Which stream should be allowed to write first?
Using Backup Order, you can assign priority to each of the parallel backup processes, the number of which is determined by the value of the "Parallel Backups" field above.
The possible option choices and what they mean is indicated below:
  • s -> smallest size first
  • S -> biggest size first
  • t -> smallest time first
  • T -> biggest time first
  • b -> smallest bandwidth first
  • B -> biggest bandwidth first
  • Try BTBTBTBTBTBT if holding disks have not been assigned a threshold (see below)
Example 1 :
A string like "sssS" which represents the priority order for four parallel backups indicates that
three dumpers will seek the smallest size hosts 
while one dumper will seek the biggest size host to backup.
Example 2 :
A string like 'BbsTt' indicates there are five parallel backup process of which:
One backup process(B) is looking for the Biggest Bandwidth occupying backups.
Another backup process(b) is looking for the smallest Bandwidth occupying backups.
Another backup process(s) is looking for the smallest size backups.
Another backup process(T) is looking for biggest Time occupying backups.
Another backup process(t) is looking for smallest Time occupying backups.
Parallel Backup Clients
Sets the number of parallel backups performed from an Amanda client. The default value is 1, which specifies that all DLEs on a client are backed up sequentially.
If an Amanda client has sufficient CPU and network resources, multiple DLEs on the client could be backed up in parallel.
Staging Area Threshold
When space on a  staging area/holding disk falls below a threshold size (the value of this parameter), Amanda limits itself to performing only incremental backups. A threshold of 20% causes Amanda fall back to incremental backups when holding disk(s) free space falls below 20%.
When there is a media error during a backup run, the backup images are still stored in holding disk. Amanda allows recovery from holding disk and backup media.
Auto Flush
Specifies whether Amanda should flush the backup images from the staging/area holding disk to the backup media before a backup run. The default value when initially installed is No. You can change the default globally for all backup sets by changing the amanda.conf(5) file's autoflush no parameter to autoflush yes. You can monitor flush activity from the ZMC Monitor page.

Setting the value to Yes may require additional space on the media volumes to account for previous backup runs, especially if you have set the Backup->When Media Per Run value conservatively. If the Backup->When Media Per Run value is greater than 1, then the additional media will be used if it is required; if not the staging area must hold any backup images that exceed the limit. For example, consider a setup where a full backup usually fills up 3/4 of the medium.  If Media Per Run is set to 1, you will usually end up with a separate pieces of media for every backup, each fiilled to 3/4 capacity. If there happens to be a day where there are two backup images in a run, the staging area/holding disk must store the backup until there is a backup run with only one image that is less than one quarter of the media size.  So if staging area space is at a premium and/or you wish to ensure that backup images always get saved to secondary media rather than the holding disk, you should set Media Per Run accordingly.

Save Button

Click the Save button before clicking to another page. These parameters can be changed even when a backup run is in progress and the change will not have impact on the active backup run. All saved changes will affect the next backup run.

If the backup set has not yet been activated (scheduled), go to the Backup Activate page.