Load Balancing - HP J3278B - SureStore CD-ROM Server/Tower 7 NAS Server Administrator's Manual

How Does It Work?
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SQL Database
The system uses an integrated SQL database to track baseline files and subsequent
versions. It keeps an index containing the compressed file details (name, directory,
date/time stamps and size) of all backed up files on the appliance.
Redundant File Elimination
The use of a database also makes it possible to identify files that have already been
backed up from the networked clients and have not been changed. This is called
Redundant File Elimination, which is a significant factor in reducing the amount of
storage space required for backup. For example, if the same version of an application
(such as the client PC's operating system or a word processing program) is run on
multiple clients on the network, the common application files are only backed up
once.
The Administrator (and sometimes client) can also exclude certain files or directories
from the backup, for example the Temp directory. File exclusions and retention
periods are discussed in more detail in the
Compression
To further reduce network traffic, client files are compressed before they are backed
up over the network to the appliance. The cumulative effect of block-level
incremental backups, redundant file elimination and file compression techniques is to
keep the network traffic requirements low enough to make daily backups of local
hard disks a practical proposition, even over comparatively slow dial-up modem
connections.
The disk storage space required on the appliance to back up all client files is greatly
reduced by the effects of redundant file elimination and compression (a ratio of 3:1 is
typical when protecting 25 clients, increasing to 4:1 with 100 clients). This
requirement grows very slowly over time due to the block-level incremental backups
and retention policies.

Load Balancing

HP SureStore AutoBackup has a built-in automatic load-balancing feature, which
ensures that only five scheduled backups are running at any one time, thus reducing
the impact on network traffic. However, manual backups (which include dial-up
Appliance Management-Capacity topic.