DELTA BACKUP

What is DELTA Backup?

DELTA Backup is a capability of BACKUP+/iX that backs up changes to files rather than entire files, a technique that can dramatically reduce the amount of time, resources, and tape or disk required for backups. Conventional backups store changed files in their entirety. This means for example, that a very large IMAGE detail dataset is backed up if any record is modified - even if the rest of the dataset is unchanged. With DELTA Backup, if a single record is changed, only that data is backed up; not the entire file. By orienting backups around changes to files rather than changed files, backups become a small subset of what they used to be.

How much faster is DELTA Backup?

When only small portions of files are normally modified in a day, and as most databases contain largely historical data, systems using DELTA Backup can experience a large reduction in backup time and tape requirements. A database backup which would otherwise require half a DAT and an hour to store could instead be backed up in a few seconds to a few millimeters of tape with a DELTA backup. In internal testing, an IMAGE dataset that has 10% of its contents modified took 85% less time to back up on a DELTA backup compared with a conventional backup.

How does DELTA Backup work?

Performing a DELTA backup is as simple as a conventional backup. In fact, it is simpler because DELTA backups take less time and fewer tapes. The operator adds the BASELINE option to BACKUP+/iX's STORE command for a full backup and the DELTA option for a partial backup.

The BASELINE option creates a conventional backup and automatically starts a monitor which tracks all write activity on the system. This monitoring is done all the time, recording the locations of the modifications to all disks on the system.

The DELTA option performs a DELTA backup, which consists of any new files created, changes to existing file attributes, and all file modifications since the corresponding baseline backup.

A baseline backup is normally done in place of a full backup, while a DELTA backup is normally done in place of a partial backup. To restore, simply use the baseline and the last DELTA backup.

Full BACKUP+/iX functionality is standard.

All the options and features of BACKUP+/iX are available with DELTA Backup, including Online Zero Downtime backup capabilities. As always, online backups with BACKUP+/iX are rolled forward on restore so that all transactions that occur up until the moment that the backup completes are protected on tape and recovered on restore.

How is DELTA Backup implemented?

DELTA Backup is implemented using ORBiT's existing online backup technology. The same proven technology that is in daily use in thousands of HP3000 sites. In fact, its operation is almost identical to that of BACKUP+/iX's Online ZDT backup, except that write transactions are monitored all the time rather than just for the duration of a backup.

Conclusion!

While DELTA Backup may sound revolutionary, it is actually evolutionary in that it is an extension of ORBiT's successful online backup strategy. It uses the same tried-and-true methodology and code that has proven itself over the past several years.