SAN's Role in Disaster Recovery

With the cost and complexity of SANs that run over IP networks declining, this powerful storage solution is an attractive option for the small and medium-sized business.

InformationWeek Staff, Contributor

August 8, 2007

3 Min Read

Storage of data and applications through a storage area network (SAN) to a remote location is one of the most effective methods of maintaining the continuity of your business in a disaster, if your headquarters or other office become damaged, destroyed, or rendered inaccessible. With the cost and complexity of SANs that run over IP networks declining, this powerful storage solution is an attractive option for the small and medium-sized business (SMB).

SAN versus NAS versus DAS

Previously, the higher cost of a SAN solution made network-attached storage (NAS) solutions the preferred networked storage method for SMBs. NAS devices are specialized servers dedicated to storage that are connected to devices through Ethernet adaptors. Simple to use, the NAS is best suited to file-based data, such as word documents and spreadsheets whereas the SAN is better suited for large amounts of data such as database files, transmitted in blocks of multiple files.

SAN and NAS solutions have introduced various efficiency methods for maximizing the storage media, making them much more cost-efficient than the traditional direct-attached storage (DAS) solutions, which are storage repositories directly attached to servers or workstations. DAS solutions do not allow for the flexible use of storage resources throughout a company or for remote backup.

SAN and NAS have evolved to be complementary rather than competing solutions. Today, most midsize to large companies have both NAS and SAN solutions. NAS solutions, backing up file-based storage, are often the front end of SANs, which in addition to backing up the NAS data to a remote disaster recovery site also back up block-level storage from database-based applications.

SAN Benefits

SAN technology can be ideal for SMBs because it:

  • Enables servers (including NAS devices that may be used to back up e-mail and documents) that run all of a company's applications and systems that rely on database entries to access and store data in centralized pools of storage devices at high speed

  • Consolidates storage devices into a common physical network where fewer devices are needed, which can lead to savings

    Simplifies storage environments by connecting servers, storage arrays, and tape drives throughout your company, whether in headquarters or branch offices, for centralized management

    Provides a separate network that can perform continuous data backup without affecting the production network

    Allows backup to more than one disk drive simultaneously (a process called "mirroring"), so if the primary disk fails, the administrator can immediately switch to the second disk

    Lets you link multiple SANs to backup to a disaster recovery site

Types of SANs

SANs use different networking protocols:

  • Internet Small Computer Systems Interface (iSCSI) converts communications between servers and storage resources into IP packets

  • Fibre Channel (FC) uses high-speed optical fiber to connect servers, storage, and tape drives

    Fiber Channel over IP (FCIP) enables storage transport over metropolitan and wide-area networks for backup to remote disaster recovery sites

SANs also rely on special storage switches. For SMBs, fabric switches create a network "fabric" of interconnections. And storage management software has become full of specialized features that facilitate backup, recovery, multiprotocol and multitransport support, scalability, and much more.

New Affordability of Remote Data Storage

Data storage in general has never been more affordable. According the Robin Harris, a storage analyst with the Data Mobility Group, the cost of a remote storage solution has in many cases come down by a factor of 10 over the past year and a half. "Partly, it's a function of having broadband everywhere," says Harris, "and it's also a function of the plummeting cost of storage components and the efficiency of IP architectures that let you interconnect to commodity servers and low cost disks."

The savings in networked storage extend to even the smallest of businesses; storage as a managed service is now available for as low as $50 per year per PC for remote data backup.

Gene Knauer writes for Cisco Systems.

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