Disk performance
All data that Data Protector backs up resides on disks in your systems. Therefore, the performance of disks directly influences backup performance. A disk is essentially a sequential device, that is, you can read or write to it, but not both at the same time. Also, you can read or write one stream of data at a time. Data Protector backs up filesystems sequentially, to reduce disk head movements. It also restores files sequentially.
Sometimes this is not visible because the operating system stores most frequently used data in a cache memory.
Disk fragmentation
Data on a disk is not kept in the logical order that you see when browsing the files and directories, but is fragmented in small blocks all over the physical disk. Therefore, to read or write a file, a disk head must move around the whole disk area. Note that this differs from one operating system to another.
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Backups are most efficient for large files with little fragmentation.
Compression
If data is compressed on a disk, the Windows operating system first decompresses the data before sending it across the network. This reduces the backup speed and uses CPU resources.
Disk image backups
Data Protector also allows you to back up UNIX disks as disk images. With a disk image backup, a complete image of the disk is backed up without tracking the filesystem structure. The disk head moves linearly across the surface. Thus a disk image backup can be considerably faster than a filesystem backup.
Disk Agent performance on Windows systems
Disk Agent performance of Windows filesystem backup can be improved by enabling asynchronous reading. Asynchronous reading improves performance of the Disk Agent when backing up data on disk arrays, especially if large files are backed up. It is recommended to perform test backups to establish if asynchronous reading will
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