Designing Storage Area Networks: A Practical Reference for Implementing Fibre Channel and IP SANs (2nd Edition)

Administrators of enterprise networks with dispersed geographical locations are often overwhelmed by tape backup requirements for remote offices and regional centers. The most common scenario is that data backup at each remote facility is entrusted to the local branch manager meaning that the manager throws in a tape before locking the doors at night. Tapes may or may not be transported off site, and tapes are rarely tested to see whether the data can in fact be restored. This is somewhat like carrying expensive car insurance but never knowing whether the insurance company will honor a claim if one is filed. Because the local branch manager or administrative assistant is probably not excited about data integrity or the tape backup procedure, tapes may not be changed, may not be properly labeled, or may be overwritten by multiple backups. Nonetheless, data on local storage is still critical to business continuance, and there may be no copy of customer information and transactions on centralized enterprise storage.

Consolidating remote tape backup operations was not feasible as long as SAN architects were constrained by the inherent distance limitations of native Fibre Channel and the exorbitant cost of dedicated or DWDM links. But IP SAN and IP gateway solutions have largely resolved the distance issue and now enable rationalized tape backup strategies based on more affordable and available IP network services, a strategy called remote vaulting.

As shown in Figure 12-12, you can use IP network services to consolidate data backup for local branch offices to a regional center. In this example, branch offices in the Midwest are connected to a regional facility in Houston, and branch offices in other regions can be backed up to the closest facility. Branch office storage can be connected to the appropriate regional center through iSCSI or iFCP gateways. The regional centers, in turn, can leverage more efficient tape libraries for both branch and regional center data.

To minimize the amount of backup traffic on each link, daily incremental backups from branch file servers would be made to the regional facility. Depending on the amount of data that must be regularly secured, the backup window and bandwidth requirements can be calculated using the formulas given in Table 6-3. Use of data compression and jumbo frames for streaming block backup data, however, maximizes link utilization and enables use of more economical wide area IP connections (such as T3). These features are available in IP routers as well as iFCP gateways.

Remote vaulting centralizes the management of data archiving and shifts the responsibility for backup from non-IT administrators to full-time IT staff. Although this arrangement facilitates verification of backup operations and secures dispersed corporate data, there is always the possibility that a regional center may suffer an outage. One of the benefits of remote vaulting over IP services is that backup data can be redirected through the IP network to an alternative operational facility. As discussed in the next section, regional center SANs can also be configured to provide mutual failover for both disk and tape data resources.