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Glossary
 Backup Software
 CRC (Cyclical Redundancy Checking)
 File Archiving
 File Compression
 File Encryption
 File Replication (File Mirroring)
 File Synchronization
 File Verification
 Unbuffered File Copy


Glossary


Backup Software

Backup programs are designed to backup files.

To "backup files" is to make copies of files (replication) and store them on a separate media to be used in case the primary files are lost or corrupted.

ViceVersa replication and archive features are designed to create secure backup copies of files and folders.

Backups are essential for all work. For important work, two or three backup sets are advisable. To be especially safe, backup sets should be kept in different locations. Backup files can be stored compressed and/or encrypted to save space.



CRC (Cyclical Redundancy Checking)

CRC is the acronym for Cyclical Redundancy Checking.

It is a type of algorithm known as a "hash". A hash algorithm accepts variable-length input and produces a fixed-length output which uniquely represents the input data. The hash is usually much shorter in length than the data it represents. A sample CRC value for a file could be ADE50E9F. In theory, no other file should produce the same hash value. ViceVersa calculates the CRC value of one file and compares it to the CRC of the corresponding file in the other folder. If the CRCs differ, the files differ. The CRC algorithm is widely used in network protocols and compression programs.



File Archiving

During File Synchronization, File Replication, File Mirroring or File Backup, older files are overwritten by newer files or they are deleted if their counterpart has also been deleted.

ViceVersa PRO enables archival of former versions of files which are changed or deleted. This is called the File Archiving feature.

By using File Archiving, when a file is overwritten or removed during a run, the old file is first moved to an archive location, locally or over the network. Files moved to the archive location maintain the original timestamp. The timestamp of when they were moved is also  encoded in the file name. Hence, multiple versions of files can be kept for a specified period of time. Extensive options in ViceVersa lets you to control how many versions of each file to keep, where and for how long: you can specify to keep old versions for X days, or up to X copies, or only for certain file names or extensions.

ViceVersa PRO also features an archive viewer tool that lets you browse the archive locations and visualize all the archived file versions.



File Compression

With ViceVersa PRO, files in Source and/or Target folders can be compressed to save space.

For example, when backing-up from a PC/Server to an external USB drive, ViceVersa PRO can keep the files on the USB drive compressed. Each file on the USB drive is compressed using the GZIP format.



File Encryption

You can instruct ViceVersa PRO to keep files in Source and/or Target encrypted (and compressed). ViceVersa PRO provides AES-256 encryption.

This feature is especially important when copying files to an external USB drive or over the Internet.

For example, if you are using ViceVersa PRO to backup files to a portable USB drive, you can make use of the file encryption feature to keep all the files on the USB drive encrypted.



File Replication (File Mirroring)

File Replication (File Mirroring) is a special type of File Synchronization, where:

  • Changed files are copied from Source to Target
  • New files in Source are copied to Target

Optionally files can be moved from Source to Target, where the source file is deleted after copy.

For more information see File Synchronization.



File Synchronization

Synchronization is an adjustment that causes something to occur or recur in unison. Specifically, File Synchronization is an adjustment to files between two (or more) locations with the goal of making sure that the locations contain the same up-to-date files. Locations can be folders on LAN, WAN, VPN, USB drives, USB keys, CD-RW, Zip Disks, etc.

Using this definition File Replication and File Mirroring (Backup) can be classified as special synchronization methods.

ViceVersa supports several File Synchronization methods:

Synchronization (Bidirectional)
This method performs a bidirectional file synchronization between Source and Target.
* All new files/ folders added to Source (single files) are copied to Target
* All new files/folders added to Target (single files) are copied to Source
* All deleted files/folders in Source are deleted from Target
* All deleted files/folders in Target are deleted from Source
* All updated files in Source (newer) are copied over older files in Target
* All updated files in Target (newer) are copied over older files in Source
N.B.: If a file changes both in Source and in Target, the file is in conflict. Conflict files need to be reconciled manually or optionally they can be synchronized automatically with the older file renamed with a timestamp.

Backup (Mirror Source to Target)
This method backs-up Source to Target by creating a mirror/replica of the Source in Target.
* All new files/folders added to Source (single files) are copied to Target
* All deleted files/folders in Source are deleted from Target
* All updated files in Source (newer) are copied to Target

Replication (Augment)
* All new files/folders added to Source (single files) are copied to Target

Replication (Refresh)  
* All updated files in Source (newer) are copied to Target (older)

Replication (Update)
* All new files/folders added to Source (single files) are copied to Target
* All updated files in Source (newer) are copied to Target (older)
N.B.: Files deleted in Source are NOT deleted from Target. This is different from the Backup method.
Optionally files can be moved to Target, that is, deleted from Source after copying to Target.

Consolidation
This method performs consolidation between Source and Target. This method does not keep track of file conflicts nor file deletions.
* All new files/ folders added to Source (single files) are copied to Target
* All new files/folders added to Target (single files) are copied to Source
* All deleted files/folders in Source are copied back from Target
* All deleted files/folders in Target are copied back from Source
* All updated files in Source (newer) are copied over older files in Target
* All updated files in Target (newer) are copied over older files in Source



File Verification

File Verification is the process of verifying that a file has not been changed and/or that two files are identical, bit by bit. ViceVersa supports both types of file verification.

You can verify that files in a specified location have not changed by creating a snapshot of one or more folders at a given time and then re-comparing the folder content with the original snapshot at later time.

You can also verify that two locations have exactly the same files, bit by bit: ViceVersa will calculate the CRC of each file to make sure they are indeed identical. A very important and common task for people working with CD creation is the verification that the data mastered is the same as the original data. For this purpose ViceVersa offers a Cyclical Redundancy Check. With ViceVersa you can determine if even one byte of data differs.

Starting with ViceVersa PRO 3, SHA-256 hash file verification can be used alongside CRC. 



Unbuffered File Copy

Starting with version 2.5 build 2507, ViceVersa PRO offers the option to perform an “unbuffered file copy” when copying files. The new option is in profile settings -> performance.

What is unbuffered file copying?

The standard file copying (the default in ViceVersa) caches file reads and writes in the file system memory. This speeds up file reads and writes, but it has an associated memory cost that may impact other applications/processes running on the system while file copying is proceeding. Especially for large files, the memory cost may be significant.

Unbuffered file copying does not cache file reads and writes in the file system memory. It is moderately slower, but it minimizes memory usage. Unbuffered file copying is preferred when copying large files or a large amount of files without impacting the system memory.

The new option Unbuffered file copy is available in ViceVersa PRO starting with version 2.5 build 2507.
This option is supported on Windows 10, 8 / 8.1, 7, Vista, Windows Server 2008, 2012, 2016 or newer. It is not supported on Windows Server 2003, Windows XP, 2000 or older.


  
  
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