CHAPTER 7 SOFTWARE ARCHITECTURES—NETBACKUP
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The general Media Server is becoming overloaded due to the particular client load.
In order to prevent the purchase of a completely new piece of hardware, the client
causing the issue is converted to a Client/Media Server, thus offloading the
backup load back to the client and freeing resources for the general Media Server.
The combination of both general-purpose and Dedicated Media Servers allows the administrator to
balance the needs of both large and small clients, crafting a solution that meets the needs of the
enterprise as a whole, but is tailored to meet the needs of individual clients. But what happens with the
limits of an individual Storage Domain are reached, and when are new Storage Domains required?
Multiple Storage Domains
There are limits to a single Storage Domain. The conditions that would trigger consideration of the
creation of additional Storage Domains are the following:
Unreliable network links
Locations separated by long network distances
Legal or organizational needs
Multiple large data centers
Performance degradation on the primary Storage Domain
When placing Media Servers at remote locations, it is important to be able to have reliable
communications back to the NetBackup Master Server in order to ensure that clients are properly
scheduled and contacted, as well as to ensure that the metadata regarding the client backups is properly
stored. If the network separating the NetBackup Master Server and the clients is either unreliable or has
noise that causes a number of network packet losses or retransmissions, the communication necessary
to make sure that clients are properly started and tracked either may not happen or happen in such as
way as to slow the backup process down. If the network issues cannot be resolved, by placing a
secondary NetBackup Master Server at the remote site, the communication becomes local, thus
bypassing the issue. For instance, if an organization has a headquarters in Seattle and a remote office in
Singapore, the connection between the two sites may (and in many cases will) have a significant amount
of loss and noise. While many applications can tolerate this, backups run locally against a Master Server
located in the Seattle headquarters will run very slowly, even if the Media Server is local to the clients. In
this case, a separate NetBackup Master Server would be recommended to ensure maximum backup
performance.
An additional effect of distance is the network latency that is induced. As distances between points
on networks increase, the round trip time of packets to travel between the sites also increases. This is
simply a law of physics problem—the speed of light is a fixed value, and it takes time for a signal to
traverse long distances. While there may be plenty of network bandwidth available, if the distances that
the network packets have to travel grow, the net throughput of the network will drop. The drop in
performance will slow the transmission of metadata from the remote site, thus reducing the overall
backup performance. While this may not be noticeable for small data backups, for larger backups,
particularly those consisting of large numbers of files, this increase in metadata transfer time becomes
apparent quickly. Again, the addition of a Storage Domain at the remote site avoids the distance
problems, localizing backups.
There also may be legal issues that force the use of multiple Master Servers. Different legal
jurisdictions place different requirements on the ability of an organization to store certain types of
information. This may be for a variety of reasons, with the net result being that it may expose the
organization to legal sanction if backups are even administered from outside of the jurisdiction. In
situations such as this, the only option is to place a NetBackup Master Server at the site and manage

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