Storage area networks allow you to offload backup processing from the primary network and host systems.
By Ron Levine
As more and more data is committed to mission-critical applications, backup has taken on an increasingly important role in IT operations. Currently, backups are typically accomplished over a LAN to a tape library. Until recently, that approach worked adequately for most organizations, but the Internet and other business-critical applications such as enterprise resource planning (ERP) and data warehousing have brought backup to a new level-one in which 24x7 operation and globalization are the norm.
"Organizations are looking for storage options that optimize the storage space available today, but can be expanded in the future. And they're looking for backup solutions that don't saturate the LAN," notes Scott Robinson, chief technology officer at Datalink Corp., a systems inte grator and networked data storage provider (www.datalink.com).
Traditional backup clogs LAN: Data is backed up over the production network via dedicated backup servers.
The most common backup approach is to back up data to dedicated tape drives or to increase LAN bandwidth and dedicate a server to the backup function. The first is time-consuming, not to mention impractical; the second is a short-term fix due to scalability issues.
SAN delivers server-less backup: Tape drives can be dynamically allocated and de-allocated across servers.
In either case, network bandwidth is used to transfer large volumes between systems and backup devices, "squeezing out" other LAN traffic. For smaller businesses, especially those that do not need continuous client access, these backup methods work well, but as more data is acquired these volumes can impinge on client functions and slow response time, especially with applications such as ERP, OLTP, and Web hosting.
Software enables shared libraries: Individual tape drives are dedicated to tape libraries. Media management is controlled by the master backup server or a separate media management server.
A better answer is a storage area network (SAN). A dedicated network specifically de-signed for data storage functions, a SAN enables enterprise-wide backup functions to take place "off" the LAN (hence the term "LAN-free"). In doing so, the LAN network is free to continue communication chores without sluggishness or disruptions, even during extensive data transfers. "A SAN is an ideal network for large-scale backups," states Robinson.
LAN-free backup can occur at Fibre Channel data rates (100MBps), compared to LAN rates (frequently less than 10MBps). Also, by removing the backup task from the LAN, bandwidth is increased, which enables applications to run more efficiently. And, lastly, because SANs are scalable, they can be easily expanded as storage requirements grow while retaining centralized management of storage devices.
There are several levels of LAN-free backup. Today, basic LAN-free technology is available. It consists of shared tape libraries with dedicated connections to individual servers over a SAN. Also available is backup software that enables multiple servers to dynamically share drives. The software allows drives to be allocated and de-allocated among multiple servers as needed, rather than on a one-to-one or many-to-one basis. This results in the need for fewer drives and libraries, and it shortens the backup window since more drives can be designated to a specified backup task.
Like direct-attached SCSI environments, basic LAN-free technology uses a shared library approach in which individual tape drives are dedicated to specified servers. Traditional SCSI connections are replaced with Fibre Channel connections, and data moves directly from application and file servers to backup devices over the SAN.
One advantage of this method is Fibre Channel's 100MBps bandwidth, which can be scaled to hundreds of megabytes per second in switched Fibre Channel environments. (Intelligent switches provide connectivity with increasing aggregate bandwidth as backup devices are added.)
Another advantage is Fibre Channel's ability to cover greater distances than SCSI (10km versus 25m). Since most disaster recovery plans involve storing large amounts of data miles away from primary facilities, backup tied to disaster recovery functions can benefit from Fibre Chan-nel's distance advantage.
Previously, there were only two op-tions: 1) to physically ship tapes to a secure building off-site or 2) to invest in costly WAN systems that are designed for messaging, not data transfer. By using channel extenders, seamless connection of Fibre Channel to ATM or T3 is now possible, extending the SAN over the WAN (SWAN). "This allows you to more simply and quickly achieve offsite storage of critical data for disaster recovery purposes," says Robinson.
In the near future, a new level of SAN backup will be available. It will include dedicated, lower-cost intelligent devices that can transfer blocks of data directly from primary storage (usually disk) to backup devices. Basically, the control involved in monitoring, processing, and moving data will be placed at the SAN in the form of a dedicated storage server.
Server-less (somewhat of a misnomer in the context of dedicated storage ser-vers) backup offers several advantages:
- The storage server is independent of the operating systems used for the general-purpose application and file servers, providing a cost-effective "thin server" dedicated to the management of data in the SAN.
- Disaster recovery is more efficient because data protection is independent of the general-purpose servers.
- The storage server centralizes data management.
- It will be possible to size the application and file servers for application functions, because they are free of backup and data protection tasks.
- Backups can be applied more broadly because data is now protected on the SAN. With server-free backup, it is much easier to consolidate and manage data.
SAN-based LAN-free and server-less backup technologies provide methodologies to accomplish backup and recovery in a more efficient, manageable, and scalable manner than traditional methods. In light of today's demanding IT requirements, it is a significant challenge to optimize backup performance while minimizing LAN saturation.
IT managers are discovering that by removing storage applications such as backup and recovery from the LAN and placing them onto a Fibre Channel-based SAN, LAN application performance can be improved, backup time reduced, and the impact of daily backups on the messaging network eliminated.
Ron Levine is a technology writer with Coast Writing, an independent firm specializing in computer application articles. He can be reached at firstname.lastname@example.org.
For more information about LAN-free and server-less backup technologies, visit www.datalink.com/papers.