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BackupWhen

Backup When

Unlike most other backup software, ZMC does not require users to lay down detailed rules as to when the backup should be performed. ZMC works through Amanda's backup scheduler which tries to maintain a consistent backup window across all backup runs by controlling the size of the backup image for each backup run.

Amanda also simplifies the configuration of the backup run schedule and specification of backup level. Instead of users pre-specifying either a Full Backup or an Incremental Backup in a particular schedule, ZMC has Full backup and 9 levels of Incremental Backup. However, ZMC does not require Administrators to specify the backup levels for each backup run. It calculates, using an internal algorithm, the levels of each DLE within the backup set for every run on a dynamic basis.

The Media In Rotation option lets you define a backup retention policy  how much media is available for rotation (see Media in Rotation below) for a single backup cycle, and therefore indirectly set a retention policy. By putting more media in rotation, you are effectively setting a longer retention policy because if more media is available, completed backups will not get overwritten as quickly by subsequent backup runs.

Backup When Page Overview

This page allows you to control how many backup runs should be performed in a given time period, and when backup runs should be scheduled.

It allows you to specify the maximum interval between two full backups (referred to as the backup cycle), in either days or months. It calculates how many backups can be completed given the backup cycle and the days and times you have identified as the backup window (See the Days/Times panel description below). This "runspercycle" value is computed conservatively: at least one full backup is performed for each object in the backup cycle no matter what. You might find that Amanda schedules more full backups in the backup cycle than required in some cases.

More information about runspercycle parameter can be found in amanda.conf(5) man page.

You should examine the Backup When page before activating a backup set; simply visiting the page sets the Backup When options to the displayed defaults for the current backup set, which may or may not be appropriate for your site.

Backup When Page Options

The Backup When page lets you control how backups will be scheduled. You can specify the overall backup cycle time, as well as the days, dates, and times within the backup cycle when backups will execute.

  • The Backup When page is divided into two panels shown below.

[need screenshot that includes "Maximum Media per Backup"]

Backup Cycle Panel

A Full Backup Cycle is the maximum time within which at least one full backup of each DLE in the backup set must happen. Amanda tries to perform full backups of the DLE as many times as possible within the backup cycle to reduce the backup recovery time. You can specify Full Backup Cycle in either days or in months.

Time Range
Select Days or Months from the dropdown for specifying the Full Backup Cycle. The GUI initially displays the default Time Range value as Days. After the Month option is selected, the ZMC right panel changes to reflect that choice.
Backup Cycle
The number of days or months within which at least one full backup for all DLEs must be performed.
Backup Time
Specifies the time of day when the backup run starts, in 24-hour format (1:00 pm is specified as 1300). This time is the same for all days and for all the DLEs in the set.
Media in rotation

In Amanda, retention policy is set on media rather than on the age of backup data. Media in rotation defines when media volumes can be overwritten (in other words, how long media volumes are retained). It sets the  "tapecycle" parameter defined in amanda.conf(5).

In case of Disk and Amazon S3 backups, media in rotation is equal to the number of slots in the device definition specified on the Backup|Where page. This is the default value for these devices.

In case of Tape and Tape changers, the Media in rotation value should be less than the number of tapes available for the backup set. The minimum value for media in rotation is the number of scheduled backup runs per  backup cycle (configured on the Backup|When page using backup run scheduler and the Backup Cycle parameter), multiplied by the maximum number of media volumes used in a backup run (configured in Backup|When page - Maximum Media Per Backup) plus one.

For example: Backups are scheduled on week days (Mon-Fri), Backup cycle is 14 days, The number of backup runs in 14 days is 10 (10 weekdays in 14 days). The minimum value of media in rotation is (10 + 1) * 2 where 2 is the maximum number of tapes used in a backup run. Of course, the media in rotation can be higher than 22, but should be less than the total number of tapes available for the backup set. The additional tapes can be used for replacement in case of media failures.

To specify a longer retention policy for backups, use the Archive button in Backup|Media page. Archived media is no longer used for backup runs and never overwritten (retained forever).

Maximum Media per Backup
Specifies the maximum amount of media that Amanda will be allowed to consume in a single backup run. This value, coupled with Media in Rotation above, effectively sets the data retention policy for the backups.

Backup Week/Month Panel

The panel on the right (titled Backup Week or Backup Month depending on context) lets you set which days of the week or days of the month to run backups.

  • When choosing a calender month, and a date such as the 31st does not exist, no back up will run on that day. It will, however, run in those months that the date is valid.

 

Example 1 Week(Days):+
Suppose Mondays and Fridays are heavy work schedule days on which days the user does not want any Backup to run.
Then tick Tuesday, Wednesday, Thursday, Saturday and Sunday.
If the user has specified a 10 day Backup cycle, and the user is starting the process on a Monday, no backup will happen that day. 
Full/ incremental backups will happen on Tuesdays, Wednesdays, Thursdays, Saturdays and Sundays. 
This will repeat for the entire cycle.
Example 2(Dates of)Month:
For another backup set, where User has selected slowly changing data, User has specified a 3 month Backup Cycle.   
The User wants the backups to run on the 1st, 10th and 20th of each month irrespective of what day of the week they fall on.
Just tick the dates 1st, 10th and 20th in the Month panel.

Note: On Solaris 10 servers, choosing all days of the week does not work from the Zmanda Management Console. The crontab entry on the Solaris 10 server must be changed manually. Change the crontab entry for amdump from 1-7 to 0-6 on the Amanda server on Solaris

Save

Click the Save button to save all changes before moving to the next page. If all the parameters have been entered correctly, following message is displayed:

Scheduling parameters have been saved for this backup set.

 

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