Both the client-side backup applications, Online Backup Manager (OBM) and A-Click Backup (ACB), are equipped with a proprietary In-File Delta technology. With this feature, the original file is required to be backed up once only, i.e. in the first backup job. Subsequently, only changes are necessary to be backed up. Thus, it can effectively mimimize the backup window. The OBM provides various options of In-File Delta to suit the need of advanced users, while there are only limited options in ACB.
The options in OBM are highlighted below.
In-file delta technology is an advanced data block matching algorithm with the intelligence to pick up changes (delta) of file content between two files.
Using this algorithm, daily backup of large files over low-speed internet connection is made possible because it requires only the changes of information since the last backup to be sent over (assuming that the full backup of the file has been saved on the backup server already).
This is what will happen in the backup of a 10 GB Outlook.pst file when it is backed up utilizing In-file delta technology:
Incremental In-file delta
Incremental Delta will facilitate ease of backup. The delta is generated by comparing with the last uploaded full or delta file. Delta generated with this method is smaller and uses the least bandwidth. However, for restoration, the full file and all deltas up to the required point-in-time are required to be restored and merged.
Differential In-file delta
Differential Delta will facilitate ease of restore. The delta is generated by comparing with the last uploaded full file only. Delta generated with this method will grow daily and uses more bandwidth. However, for restoration, the full file and a single delta is required to be restored and merged.
This allows you to define the size of block used when detecting changes between last full or delta file and the file to be backed up. In general, smaller block size
- produces a smaller delta file due to a more precise comparison
- requires more processing power on the client machine
- may lead to slower comparison.
On the other hand, large block size
- produces a larger delta file due to a less precise comparison
- requires less processing power on the client machine
- may lead to faster comparison.
For most cases, the default [Auto] setting in AhsayOBM will select the optimal block size for each file (depending on the size of the file).
Apply to files (Minimum Size)
It is for you to define the smallest file size a file must have before the use and application of In-file delta technology. If the size of a file that is being backed up is smaller than the [Minimum File Size] setting, In-file delta technology will not be applied to this file and the whole file will be uploaded to the backup server. It is not necessary to perform In-file delta backup on small files because backing up the whole file does not take long. Backing up the whole file instead reduces the time required to restore the file.
This allows you to define whether to enable the delta merge feature for the corresponding backup set. The delta merge feature combines the full and delta files (differential or incremental) on the backup server or backup appliance into a single full file. The advantage of using delta merge is it will speed up the restore of files. As a single 'merged' file can be restored faster than a file consisting of full plus related incremental files, which may require a lengthy merging process after restoring to a client machine. Delta merge can be applied to full and differential or incremental delta files which reside in the data area. The criteria for file merging are governed by the retention policy setting for the backup set.
Advance In-file Delta Type
This feature allows you to override the standard in-file delta schedule by defining custom in-file delta processing at specific points in time. This is especially useful for users who want to limit their backup on specific day. For example, incremental delta backup on weekdays and differential delta backup on Saturday.
*** Note *** Using Advanced In-File Delta will disable Delta Merging.