Disk-Assisted Backup Whitepaper

backup. The restore is significantly simpler and quicker than that without the synthetic full backup. In

the figure, both possible (1+2) restore chains are shown.

Figure 6.

In Figure 6, a synthetic backup was performed and then copied. This provides additional safety. The

restore to the latest possible state can use any of the three different (1, 2, or 3) restore chains shown.

By default, HP Data Protector software selects the optimum restore chain, which normally includes the

synthetic full backup or its copy.

Distributed file media format (DFMF)

With HP Data Protector software 6.0 a new media format is introduced, named distributed file media

format (DFMF). This format can only be used with the HP Data Protector software File Library and is

by default not enabled.

Without this format HP Data Protector software writes all data and catalog segments into one file. This

is done per session; hence each session creates its own file. With the new media format, pure data

blocks are written into different files. This is done for each file, bigger than the used block size

(default 64 KB); hence for each backed up file, a dedicated file on the File Library is created, which

holds the data blocks.

If a consolidation session is performed on backups that are all located in the same File Library, the

data that will be consolidated is already stored in one or more media files. The new DFMF concept

tries to reuse those files; hence instead of copying the data blocks, they are only referred by way of

pointers. Therefore consolidation sessions, creating virtual full, do not copy the files hosting the data

blocks, instead, the new session only refers to them by way of pointers. Note that only consolidation

sessions are using pointers; normal backups, both full and incremental, are always creating new data

block files.

HP Data Protector software object consolidation prerequisites

The following prerequisites must be fulfilled to perform a synthetic or virtual full backup in HP Data

Protector software :

• All the backups that will be consolidated were performed with the enhanced incremental backup

option enabled.

• All incremental backups that will be consolidated reside in the same File Library.