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
Application Traffic
Clients | Application |
Servers |
Backup
Backup
Servers
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.
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