Partition Manager 8.5

Offline versus Online Backup

In the course of time there have been developed various methods of backing up data. Despite different work concept, all of them can be divided into two principal groups: offline (cold) and online (hot) backup techniques.

As the name infers, offline backup can only be accomplished when the data is in consistent state (the operating system and all the applications are completely shut down). Actually it is the most preferable way of image creation, since backup software obtains an exclusive right to process data that guaranties high level of operating efficiency. However an offline backup is absolutely out of question when dealing with 24/7 production environments.

In contrast, online backup enables to create a consistent snapshot even as the data is currently modified. Online backups are particularly useful for systems with high availability requirements, but they won’t be accomplished until all active transactions are complete. The point is to provide a coherent state of all open files and databases involved in a backup, taking into account that applications may still keep writing to disks. As a result an online backup cannot boast high operating speed.

Our program supports both offline and online methods of image creation. As far as online backup is concerned it offers its own hot processing algorithm together with the possibility to use snapshot technologies provided by the Microsoft VSS framework.

Paragon Hot Processing Technology

Paragon Hot Processing is an online backup technology for Windows NT+ family operating systems. Developed back in 2001, nowadays it is integrated with all backup solutions offered by the company.

Paragon Hot Processing is not exactly a snapshot technology, though it has much in common with it. During an online backup, the program uses the kernel mode driver HOTCORE.SYS to intercept and control disk write activity of applications and the operating system. The hotcore driver as an integral part of the program is installed during the setup procedure (that’s why the system reboot is required to complete the setup procedure). For the most part the driver is in the idle mode until it is activated with the program. While in this mode it bypasses any calls having no effect on the overall system performance, but a few kilobytes of the system memory.

Paragon Hot Processing technology offers backup of locked partitions and hard disks under Windows NT+ family operating systems providing both high operating efficiency as well as low hardware requirements.

Volume Shadow Copy Service

Microsoft Volume Shadow Copy Service (VSS) is designed to provide the backup infrastructure for the Microsoft Windows XP/Server 2003 operating systems. It offers a reliable mechanism to create consistent point-in-time copies of data known as shadow copies. Developed by Microsoft in close cooperation with the leading backup solution vendors on the market, it is based on a snapshot technology concept.

Initiated by a VSS aware backup utility, VSS creates snapshots for the selected volumes and represents them as virtual read‑only devices, called volume shadow copies. Once the shadow copies are created, the backup utility starts processing the data while applications keep writing to original volumes.

Unlike Paragon Hot Processing the VSS technology provides a unique possibility to make a synchronous snapshot of multiple volumes. This very feature can be particularly beneficial when backing up active SQL Server 2003, Exchange 2003 or Oracle databases located on multiple volumes the way it is recommended by Microsoft to improve the level of database performance and reliability, thus providing 100-percent data consistency.