• Quota (maximum capacity) must be entered in the URL Resource definition. This may be changed as needed. The quota should be set to less than the available free space on the FTP server.
• Multiple archives per medium utilizes archive expiration times and lazy reclamation to maximize the number of archives stored for maximum safety.
• Compression and optional encryption are supported.
• Full file checksumming, for maximum data integrity, is supported.
• Instant File Restore is available from any archive. It is not necessary to read through an entire archive to restore individual files and directories.
• MySQL™ hot backups are supported.
8.4 - Theory of Operation
For the most part, these backup resources are very similar to more conventional ones such as tape or DVD. However, there are a few points you should be aware of before using them.
Segments
In a tape backup, BackupEDGE streams the data directly on to the media. In FTP backups,
BackupEDGE streams the data into archive files on the FTP site. This potentially subjects the
files to filesystem size limitations and ulimit or other arbitrary operating system limitations. To work around these limits, BackupEDGE automatically segments archives; that is, it divides one logically long archive into short archive files (called segments) that can be managed by the operating system using the storage device. By default, these segments are 1 gigabyte -1 block in length1.
Medium Archive Behaviour
URL
The process will attempt to create a new archive. If starting a new segment would cause the quota to be reached, the oldest expired archive will be erased in its entirety (all segments). If starting a new segment would exceed the quota and no more expired archives exist, the backup will FAIL.
BackupEDGE can write multiple archives to FTP servers, and each archive may contain multiple
segments. BackupEDGE handles segments automatically, and provides tools for managing the segments. To maintain consistent archives, the individual segments should never be manipulated by operating system commands. This is why segments do not have names that make sense to humans.
Quotas
Each URL Resource is assigned a storage quota. BackupEDGE will not attempt to use more storage on the FTP server than that assigned by the quota.
Retention Times
By default, all archives created to a URL Resource using the Scheduler have a retention time (or expiration time) of one week. They will not be erased automatically until the retention time is up, but will not necessarily be erased just because its retention time is up. An archive past its
retention time is called an Expired Archive.
Space Reclamation
Archives are retained on FTP servers at least until their expiration time has passed. After that, they are deleted in one of two ways...
Lazy Reclamation Enabled (Default)
If Lazy Reclamation is enabled, archives will remain on the server as long as possible, just in case they may be needed even after their retention time is up. This allows maximum space utilization on the server. For an archive to be deleted...
• The retention time must be up, i.e. it must be an Expired Archive.
• Adding a segment to a new archive would cause the defined quota to be exceeded.
If both conditions are true, the oldest Expired Archive will be deleted in its entirety. This process ensures that a maximum number of older archives are available on the URL Resource.
If the quota is reached and none of the archives has expired, the backup will prompt for additional media.
By default, each backup in a Scheduled Job has a Retention Time of 1 week. This is may be changed on a per-schedule basis in the default simple Scheduler, and on a per-backup basis in the advanced Scheduler.
Lazy Reclamation Disabled
Disabling Lazy Reclamation (un-checking the Lazy Reclmatation field in the Resource
Definition) configures BackupEDGE to check for and immediately erase all expired archives any
time a new backup is started to the URL Resource. Only unexpired archives will be retained. This allows only the minimum required amount of space to be used, while still retaining as many archives as are needed.
Note that usually, if you are backing up multiple machines and/ or schedules to the same FTP site, you will create multiple Resources, one per machine/schedule combination. Each Resource would use a different directory on the FTP server and have a different quota. A typical schedule would look like this:
Sample FTP Backup Schedule
This Schedule will perform Monday through Friday backups. In the example, a five backup rotation will be created. Because of the one week default retention, Expired Archives (those older than one week old) will be retained on the FTP server at least one week, and possibly longer based on the Lazy Reclamation flag in the Resource definition. If the quota is reached and none of the archives has expired, the backup will fail.
Changing the retention time in the Schedule to 2 weeks, three weeks, etc. allows easy creation of multiple minimal storage rotations.