In-File Data

Quick Backup is fast because of In-File Delta Advanced Technology!

The greatest obstacle with large files backup via the Internet is massive backup time.
In-file delta technology is an advanced data block matching algorithm which has the intelligence to detect the changes between two files. With this technology, sub-sequence the Quick Backup will only upload the changes to the file, or in other words delta of a file to the off-site backup server.

This is especially useful for backup of large file over low-speed internet connection.
For example, backup of a 10 GB Outlook.pst file with In-file delta enabled.

On the initial backup, the full Outlook.pst files (10 GB), along with its checksum file are backed up to the backup server (which can be done over the internet or with the Seed Load utility).

On sub-sequence backup, the backup application would first download original checksum that exist on the backup server, and compare the checksum file checksum listing of all data blocks of the full backup file (or last incremental backup file) from the backup server and use it to pick up all changes that have been made to the current Outlook.pst file.

Changes detected are then saved in a delta file which is uploaded to the backup server. A new checksum file is generated and also uploaded. (This delta file is assumed to be small because the content of PST files doesn’t change a lot during daily usage).

Subsequent backups of this 10GB Outlook.pst file will go through step ii and step iii again. As explained, only a small delta file and checksum file will be uploaded to the backup server.

With in-file delta technology, daily backing up of large file over low-speed internet connection is now possible.

You can choose Incremental or Differential!

 

 

 

 

Incremental in-file delta type

Incremental Delta will facilitate ease of backup. The delta is generated by comparing with the latest uploaded full or delta file. The delta file generated is the smallest possible and uses the least bandwidth during backup. For restoration, the full file and all delta files up to the required point-in-time is required to restore the file to a specific point-in-time.

Example:
If you are adding around 100MB changes to a 10G Outlook.pst everyday.
After the first full backup job, the client software will continue to generate and upload delta files instead of uploading the full file until either one of the following two rules are true:

1. Number of deltas generated since the last full backup is greater than the [No. of Delta] setting.
2. The delta ratio (the ratio of the delta file size against the full file size) is greater than the [Delta Ratio] setting.

Using incremental delta, the delta generated by comparing the current file with the latest uploaded full or delta file is around 100MB.
Since the delta file size is around 100MB daily, the delta ratio (around 1%) will not trigger a full file upload. Instead the client software will continue to generate and upload delta files until day 102 (assuming the full file was uploaded on day 1) when the number of deltas generated exceeds the [No. of Delta] setting and triggers the upload of the full Outlook.pst file. You can disable the [No. of Delta] and [Delta Ratio] if you do not want to upload the full file.
All delta files are generated with respect to changes made since the last incremental or full backup. This means that the last full backup file and ALL incremental delta backup files are required to restore the latest snapshot of a backup file.

Differential in-file delta type

Differential Delta will facilitate ease of restore. The delta is generated by comparing with the latest uploaded full file. The delta file generated grows daily and uses more bandwidth during backup. For restoration, the full file and a single delta file is required to restore the file to specific point-in-time.

Example:

If you are adding around 100MB changes to a 10G Outlook.pst everyday.
After the first full backup job, the client software will continue to generate and upload delta files instead of uploading the full file until either one of the following two rules are true:

Number of delta generated since the last full backup is greater than the [No. of Delta] setting.

The delta ratio (the ratio of the delta file size against the full file size) is greater than the [Delta Ratio] setting.

Using differential delta, the delta generated by comparing the current file with the latest uploaded full file is around 100MB for the 1st delta, 200MB for the 2nd delta, 300MB for the 3rd delta and so on.
Since the delta file grows by 100MB daily, the delta ratio for day 52 (delta file size is approximately 51x100MB=5.1GB, assuming the full file was uploaded on day 1) being over 50% exceeds the [Delta Ratio] setting and triggers the upload of the full Outlook.pst file. You can disable the [No. of Delta] and [Delta Ratio] if you don’t want to upload the full file.
All delta files are generated with respect to changes made since the last full backup file (i.e. differential backup). This means that only last full backup file and the last delta file are required to restore the latest snapshot of a backup file. This means that other intermediate delta files are only required if you want to restore other snapshots of a backup file.
Differential in-file delta backup has the benefits that a corrupted delta file would only make on particular version of a backup file non-recoverable and all other backups created by other delta files of the same file would still be intact.

Block Size

The block size defines the size of data block being used to detect the changes between the last full or delta backup file and the file sitting on the local computer right now. In general, the smaller the block size, the more likely a matched data block can be found between the last backup file and the file on local computer. It, therefore, produces a smaller delta file but it would require more processing power to detect these changes. On the other hand, in-file delta backup running with larger block size will run faster but this will generally produce a larger delta file.
In most case, the default setting [Auto] will choose the optimal block size for each file (depending on the size of the file) for you.

Minimum File Size

The [Minimum Size] setting defines the smallest file size a file must have before the use and application of in-file delta backup technology.
If the size of a file that is being backed up is smaller than the [Minimum Size] setting, in-file delta backup technology will not be applied to this file and the whole file, instead of just the delta file, will be uploaded to backup server. It is not necessary to perform in-file delta backup on small files because backing up the whole file does not take too long anyway. Backing up the whole file instead reduces the time required to restore a backup file.

 

 

 

 

 

 

Default size is 25MB.

Delta Merging

When the delta merge feature is enabled, full file and incremental delta files are merged according to the delta merge policy configured.

The delta merge process relies on the retention policy setting when deciding when to merge incremental delta files with the corresponding full file.
Delta merge can only be applied to full and incremental delta files in the current area, but not in the retention area. The criteria for file merging is governed by the retention policy setting of the corresponding backup set.
Any reference to retention policy in the context of delta merge implies delta merge policy.
An advantage of using delta merge is that it will speed up the restore of files. As a single (merged) file can be restored much faster than a file consisting of full plus related incremental files, which will require a lengthy merging process after restoring to a client machine.

Please note that when the delta merging feature is enabled, In-file delta settings of the corresponding backup set, such as [In-File Delta Type] and [Upload full file when] are ignored.
There is no delta merging feature for Local Copy backups.

Delta merging process

A delta merge will take place after a backup job is completed, the backup client application will initiate a delta merge request at the end of a backup job, if there has been an incremental delta upload.
As part of the request, the backup client application will upload a copy of the backup set encryption key to the backup server which is hashed for security purposes. Once a merge request is received by the backup server it will be placed in the delta merge queue.
A background job is used on AhsayOBS to identify any incremental delta files that are out of retention period and merge them with the full file; this process handles one merge operation at a time.

Delta merge for a file can only be triggered once every 24 hours.
The 24 hour period is calculated from the start time of the previous delta merge and the start time of the current merge.
As backup sets enabled with delta merge share a single setting, any changes in retention policy will impact on the availability of snapshots that can be restored from both data and retention area. Before enabling the delta merge feature please review your data restore requirements carefully.
To enable the delta merging feature, select the [In-File Delta] tab in the [Backup Setting] menu, and select the checkbox beside [Enable delta

Uploading full file again

Number of Delta

The number [No. of delta] setting defines the maximum number of delta files from the same full backup file to be generated and backed up to the backup server before a full backup (the whole file) of this file is uploaded to the backup server instead.

For example, if you have created 100 delta files from the full backup file already and the [No. of delta] setting is set to 100, the next backup will upload a full backup file (the whole file) instead of just the delta file. However, if the [No. of delta] rule is disabled, it will keep generating delta files and uploading these delta files to the backup server until the other delta rule forces a full backup (i.e. delta ratio exceeded). This setting is here to make sure that there will always be a full backup file after a certain number of delta files have been generated.

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