In-file Delta Compression of Databases and Virtual Images

Backup Virtual Machines and Databases using BackupChain's In-File Delta Compression

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With BackupChain you can create a backup of virtual machines on Hyper-V, VMware or Microsoft Virtual PC/Server while they are running with the simple settings outlined below. In addition, by switching on in-file delta compression you can keep daily (or even hourly) copies of your entire database or virtual machine images without wasting backup space.

Why Use In-File Compression? Save storage space. After a full delta is generated, the next delta contains only the changes compared to before; therefore, your second backup of your 128 GB virtual VM may end up being just 50 MB! Assuming that the average daily change is about 50 MB, then backing up your virtual machine every day for the entire year will only require 50 MB * 365 =  18 GB, that's less than 15% of the drive's total size!

Save Time and Bandwidth! When you switch on BackupChain's FTP functionality, you can send that 50 MB off to a FTP server on the Internet in very little time compared to resending the entire 128 GB.

Delta Compression is necessary for efficient online backup because it reduces storage space as well as bandwidth requirements. BackupChain compresses and encrypts your delta files if you need it. Because BackupChain ships with a built-in FTP server, you can set up your own online system with ease.

How to Set up Delta Compression for Virtual Machines and Database Servers:

You can either create new task or modify an existing task.

To create a new task, click on New Task and the backup wizard will appear (click to zoom):

hyper-v backup software

Once you clicked through all settings, click Save and Edit and then navigate to File Types to enable delta compression for additional file types if necessary:

 

file type settings

As shown in the screenshot above (click to zoom in), the file extensions *.vmdk (VMware) and *.vhd (Microsoft Virtual Server and Virtual PC) are added with a minimum file age of 1 hour. For databases, select *.LDB and *.MDB (Microsoft SQL Server) and all other extensions that are necessary depending on your database server. The one hour minimum file age means that BackupChain will backup these virtual drives one hour after their last change, not earlier. In addition to this setting you should set the backup task schedule to 'Continuous' to ensure files are scanned periodically. By specifying a minimum file age you avoid backup up every single change that may occur within seconds.

If the files are locked, for example because the database or virtual machines are running, BackupChain will use Microsoft Volume Shadow Copy to unlock them and access a safe background copy. Ensure that VSS Writers are available and switched on for your system (e.g. SQL Server VSS writer, etc.).

Next, it is necessary to explicitly switch on delta compression for each file type by checking 'Turn on delta compression for this file type'. The setting 'Versions to keep' in the above example is set to 365, meaning that we wish to retain up to 365 copies of all virtual machines. Then continue to the Delta Compression tab (see below, click to zoom):

delta compression settings

Since virtual machines and database files tend to get fairly large, it is important to select a large data block size > 1MB.

There are two types of Deltas available: Incremental and Differential:

Incremental Deltas give you the smallest possible delta because only the file change compared to the previous version of the file needs to be stored.

Differential Deltas store the difference compared to the last full version of the file.

Incremental deltas are usually more economical with storage but it may take more time to restore the nth version of a file because every single version needs to be recovered sequentially. Differential deltas are much faster to restore because BackupChain restores first the last full version of the file and then applies only one single delta to it. The tradeoff of differential deltas is that they tend to require more storage.

Data Block Size is the size of the blocks that the delta algorithm handles. When dealing with large files it is better to set this number high to reduce the total number of blocks. Keeping the number of blocks to a minimum reduces overhead but may lead to larger delta files. A 1MB block size suits generally well for virtual drives up to 32GB. Larger values can be entered if necessary.

Recreating full delta versions is necessary when working with incremental backups because it would take days to restore hundreds of incremental deltas one after the other, especially if the file is relatively large (>10 GB). In the above screenshot example, BackupChain will write out a full delta file every 5th cycle to keep restore time to a minimum.

Under the Compression tab, you can switch on compression and switch on encryption if needed. Delta files are stored in a proprietary format (*.FastNeuronDelta) and are protected with AES encryption when it is switched on.

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Please email us your support requests: support@backupchain.com