As you develop a new plan for the business continuity of storage networks, or modify an existing plan, there are key areas to consider that will enable the network to continue operating in a variety of circumstances. Among these are the integration of business continuity requirements into capacity planning disciplines, the effective tracking of storage system and device outages, and a realistic evaluation of sustained outage assessment.
On the technical side, the ability to effectively monitor performance and capacity of existing configurations, though challenging, is imperative (see Chapters 22 and 23). This includes an inventory and evaluation of the existing capabilities of storage functions (for example, RAID level support, environmental limitations, and remote settings).
The main design considerations for the SAN are the configuration of core switching and estimates regarding new redundant switches for recovery processing. Within this category are the number of expansion ports, the availability of dynamic ports and paths, and port utilization estimates. Secondary to the core switch is the storage strategy to facilitate replication of recovery data, the time and state requirements of replicated data, and the synchronous (or asynchronous) nature of this process. Thirdly, is the ability of the reconfigured infrastructure to handle the adjusted I/O workload.
It should be noted that many additional items are required to develop, design, test, and implement a full business continuity plan for SAN. These include server sizing, recovery site preparation, application portability, and required application software and subsystems, such as compatible file systems and database systems. Although outside the scope of this book, these items should be integrated into a well-designed plan and not overlooked.
NAS will be the most deceptive in preparing for business continuity planning. Given its ease of installation and maintenance, its possible to overlook its potential problems. Design considerations should center on the requirements for data redundancy, and result in configuration to mirror production data either synchronously or asynchronously. This requires a NAS-to-NAS device configuration and should be driven by the requirements for complementary or compatible devices.
In addition, it will be necessary to provide redundant capacities and daily backup protections for respective devices. Over and above these are fundamental considerations to ensure that capacities are allocated so that as a failover scenario is implemented, the realities of the continuity plan workload can be handled.
Redundant configurations that are local must adhere to cabling limitations. Remote configurations must maintain a strict level of monitoring to ensure the data maintains the prescribed level of consistency. Local redundancy costs can be much less than remotehowever, full failover clustering systems can move costs well into the range of remote disaster recovery services.
It is important to understand whether the configuration will support a local system or unit outage, or have to be part of an entire disaster recovery scenario. This simple characterization of the business continuity solution will result in a configuration direction focused on the appropriate support.
Trying to not overlook necessary components in assembling an alternative storage configuration to support a business continuity solution is a constant worry. However, the successful operation of disaster recovery storage configuration may never see production processing and hopefully never be used in a disaster scenario. Even so, these are configurations that certainly should be tested. A successfully tested configuration should provide the required information of configuration settings, files, and addressing schemes including storage arrays, switch ports, LUN assignments, and zonings used.
Many components of the backup storage infrastructure may have to be re-configured back into a production environment or used in an alternative configuration. If this is the case, or might be the case, be sure you document the configuration information for later access. Its best to rely on procedures and current information than ad hoc expertise to reinvent the backup configuration during each disaster recovery test.