Disaster recovery - saving your business

Scheduling tape backups for both efficiency and completeness is essential to any tape-backup plan. When daily backups become unmanageable, it's time to consider both incremental and differential backup schemes.

In many cases, however, tape backup is just not enough, especially when the company in question serves millions of people every day. That's when a host based replication is an effective solution.
In recovering from an IT disaster, timing is everything.

Costs inconvenience can mount quickly with each minute that access is denied to critical systems, networks and data. That's why it's essential to have a plan for getting your data back, whether that means replicating your entire network or just the critical pieces of it, using company-owned or outside resources.
Downtime costs vary from industry to industry, based on dependency upon technology and typical labour costs.

Companies that are the most dependent upon automated systems, such as energy, financial services and telecommunications enterprises, accrue an average of nearly $8 million in losses for every hour of downtime, based on lost revenue and employee idling. IT-dependent manufacturing companies suffer per-hour revenue losses of $3 million. Health care, media and hospitality/travel companies, less dependent upon IT infrastructure, lose $1.5 million of revenue per hour.

But vulnerability is a relative thing. Dollar losses may not be your primary concern if you're in charge of, say, a utility company whose IT outages can leave customers without heat. Protracted outages also can translate into a loss of customer confidence. That's a major vulnerability for even the smallest just-in-time manufacturer or e-business.

If your organisation can handle the hefty price, you can attack the problem of business continuity by replicating everything in your production environment at an alternate backup disaster recovery facility.

You can use high-speed networks and storage and server mirroring to provide instantaneous failover from one site to the other for hiccup-free disaster recovery.
Most companies, however, can't afford a strategy of full redundancy. For these enterprises, specialised vendors can help replace critical IT infrastructure.

Traditional business recovery-service vendors, such as Comdisco Continuity Services, Hewlett-Packard Co. Business Recovery Services, VERITAS Software and IBM Business Continuity and Recovery Services, make up one part of this market. The theory is that hammering out recovery logistics before an interruption occurs will speed recovery in the wake of a lightning strike, flood or other natural disaster.

Modern storage-recovery requirements present a problem for conventional business-continuity planning. With the proper logistics, provisions can be made to replace system platforms, networks and even user work areas quickly, but the real key to recovery is time to data. How rapidly data can be restored for use by business applications, decision-makers and customers is the ultimate determinant of successful recovery.

Given this fact, the proliferation both in volume of data and in the type and topology of storage platforms within an enterprise can create requirements that will make or break the efficacy of all other recovery plans.

Platform Proliferation
Topologies for storage within the corporate IT infrastructure have proliferated. DAS (Direct-Attached Storage) is out; networked storage, including NAS (Network-Attached Storage) and SANs (Storage Area Networks), is in.

Networked storage solutions will show a robust combined annual growth rate of 67 percent to 2003, according to IDC, while the growth rate for storage solutions based on the traditional server-with-attached-storage-array model will decrease by 3 percent during the same period.

Of course, companies rarely mothball older, still-serviceable storage components when they bring new storage components in-house. Thus, the move to NAS and SANs merely increases the number of platforms on which data is stored as well as the number of targets to which data must be restored following a disaster.

Networked storage solutions can pose special difficulties that significantly degrade the already-marginal speeds of most tape-based data-restoration solutions. For example, in a SAN, physical disk devices are increasingly "managed" by storage domain servers, storage routers and/or software-based virtualisation products that work to deliver virtual volumes to SAN-attached servers.

These provide the real value of a SAN: They enable dynamically scalable volumes comprising many distributed physical disks and array partitions that can be grown or shrunk to meet changing storage demands.

In a storage-restoration situation, these SAN virtualisation layers must also act as interpreters, or filters, that direct data streams back to the target disks and partitions that make up the virtual volume where data normally resides.

This process introduces several thorny issues related to how data-layout records are maintained, and how the records can be interpreted efficiently by the virtualisation products so that data is restored correctly and quickly.

VERITAS Software has launched initiatives to address these issues. Ironically, early adopters of SAN technology often cite efficient backup as one of their primary reasons for embracing the topology. Restoration, however, is an important limitation to SAN efficacy especially as virtualisation approaches come to the fore.