21.7 Tuning Automatic Backups

You must balance the number of backups you keep on disk with the need to not exceed available disk space. To help manage the amount of disk space your archival and hot backups take, you can change the settings of various ics.conf parameters that determine how many copies of the backups you keep at one time and where the disk space threshold is that will trigger clean up of the older copies.

There are three types of parameters that can be adjusted for the each backup type, archival and hot backup:

• mindays – The minimum number of days worth of backups held on disk.

• maxdays – The maximum number of days worth of backups held on disk.

• threshold – The percentage of disk space used. This is used as a trigger point.

Calendar Server keeps backups for the maximum number of days possible without going over the threshold on disk space. So if the current backup is going to push the disk usage above the threshold, the system will purge the oldest backup copy and see if disk space usage goes below the threshold. It will continue to purge old backup copies until either of the following conditions is met: removing another backup copy would bring the number of backups on disk below the minimum number of backup copies, or the disk space usage falls below the threshold.

Therefore, you can manage the amount of disk space backups use with the threshold parameter. And conversely, you can manage how many backups you keep on disk by adjusting the amount of disk space and copies allowed.

The following table lists the ics.conf parameters that control the disk space and number of backups kept on disk.

Table 21–3 ics.conf Parameters Used to Set Number of Backups Held on Disk

ics.conf Parameters	Default Setting	Description
caldb.berkeleydb.hotbackup.mindays	3	Minimum number of days of hot backups held on disk.
caldb.berkeleydb.hotbackup.maxdays	6	Maximum number of days of hot backups held on disk.
caldb.berkeleydb.hotbackup.threshold	70	Percent of disk space used for hot backups. Triggers purge of oldest copies when exceeded.
caldb.berkeleydb.archive.mindays	3	Minimum number of days of archival backups held on disk.
caldb.berkeleydb.archive.maxdays	6	Maximum number of days of archival backups held on disk.
caldb.berkeleydb.archive.threshold	70	Percent of disk space used for archival backups. Triggers purge of oldest copies when exceeded.