Cisco Systems MDS 9000 Manuel D’Utilisation

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conjunction with backing up to tape. Replication technologies also provide multiple options suitable for varying
application requirements. Although replication can help you to recover from a catastrophic failure faster, it does have
a limitation of replicating corrupt data along with valid data. Therefore, there will always be a need for tape backup
as a way of archiving valid data. This paper primarily focuses on tape backup technologies, architectures, and options
as a component of an overall DR plan.
Tape Backup
In today’s enterprise environment, most application servers are directly attached to a dedicated tape drive via a
parallel SCSI connection. Dedicated resources are expensive to both deploy and maintain since the number of tape
devices to be managed increases in direct proportion to application servers. However, directly-attached tape drives
guarantee performance because that server is the only one who uses the drive. Cost considerations caused a migration
to network backup models where tape drives were placed on a LAN and shared among multiple servers. A typical
LAN based backup scenario is shown in the figure below. In this model both data and backup traffic traverse the
same LAN. The networked model for backup optimizes tape utilization and enhances manageability but introduces
concerns listed below.
Figure 1
First, large volumes of data being backed up increases traffic on the LAN and may cause degradation in application
performance. Backups are generally performed off-hours in order to minimize interruption to data traffic. Growing
data volume leads to a longer backup window that can potentially extend into business hours. Globalization of
enterprises continues to shrink available time windows for backup due to 24x7 uptime requirements. Secondly,
sharing LANs for backup and application traffic may result in backup interruptions causing backup jobs to fail
altogether. Thirdly, backup and data applications sharing the same LAN can often prove costly as a firmware upgrade
or instability in one application environment can lead to an outage in the other as well. To alleviate these potential
conflicts in a common LAN, administrators proposed a separation in application and backup domains. In newer
implementations, customers are migrating towards LAN-free architectures to segregate backup traffic from
applications as described below. A large number of customers have started to deploy dedicated storage networks
for backup.
Application
Servers
Backup
Servers
Clients
Application Traffic
Backup