How to Take Data Storage Traffic Off the Network

FRAMINGHAM (04/10/2000) - Eager to relieve traffic from the network and server, network professionals are looking to serverless and LAN-free backup, two emerging technologies made possible by storage-area networks (SAN) and network-attached storage. As the amount of data storage grows, the time it takes to back it up increases and the amount of traffic it produces can slow down the network. Add to that the tedious nature of network backup and you have a situation that is rapidly becoming an administrative nightmare.

LAN-free backup promises to relieve networks of traffic destined for storage by moving the back-up data from networks and putting it on servers connected to storage devices by switches or routers on Fibre Channel networks.

In LAN-free backup, a Fibre Channel network adapter is installed in each server. The adapter connects to the server's PCI bus and its applications on one end and to a Fibre Channel hub or switch on the other end via fiber-optic or copper coaxial cable. The hub attaches to a single or multiple tape libraries or disk arrays. Other network servers attach to the hub in the same fashion.

Software residing on a server spawns the back-up process on each of the other servers. Data flows from the storage arrays to the back-up device located on the Fibre Channel storage network, bypassing the corporate network. A number of storage hardware vendors, including EMC and IBM Corp., and back-up software vendors Computer Associates International Inc., Veritas and Legato, are implementing the technology in their products.

"Every user has a back-up problem that is getting worse, not better," says Steve Duplessie, an analyst with Enterprise Storage Group in Milford, Massachusetts. "LAN-free and serverless back-up technology allows users to back up the network and, more importantly, recover data at 10 times the speed of current methodologies, while freeing up the LAN, system CPU and memory cycles."

The idea is catching on.

"We've been exploring [LAN-free and serverless backup] for about eight months now," says Stephen Lopez, director of IT architecture at the National Board of Medical Examiners in Philadelphia. "When we drew our back-up process logically, we saw that the data was leaving the server and going out on the wire to only go back on the server to be backed up. It was ridiculous."

Lopez' daily backup, which amounts to about 500G bytes, takes 14 hours.

Victor Loy, a LAN engineer at Lockheed Martin in Little Rock, Arkansas, manages a Windows NT network. "LAN-free [technology] will give me better availability to back up," Loy says. "When I back up now, I put a [150G-byte] load on the network. If I can add another network adapter in the server and run the backup on a separate independent network, it will free up the primary network for the users that are on it."

Duplessie adds, "LAN-free backup simply eliminates the LAN from the back-up path. It automatically switches a tape drive from one node to another directly, without moving the data from the second node over the LAN." Duplessie says that while LAN-free backup is an improvement over traditional LAN-based backup, "it still sucks the life out of the server and will potentially perform 10 times slower than serverless technology."

Serverless backup takes LAN-free backup a step further. The technology removes the processing from the server and moves it to an intermediate device such as a Fibre Channel switch or router, or free workstation, freeing the server to process information requests and perform other tasks.

The back-up application, running on the intermediate device, queries the server and identifies the information that needs to be backed up. The server sends this information to the back-up application. The application, which has access to the Fibre Channel storage devices, then performs the copy block by block from disk to tape, also dubbed extended copy or the third-party copy specification. Third-party copy became a standard when it was added to the SCSI-3 standard and adopted by the American National Standards Institute and the Storage Networking Industry Association.

Lopez is looking for an application that will back up his Windows NT and Solaris server networks. "I can take my Sun storage, connect it to a Fibre Channel router and also take my Compaq [Windows NT] storage, and hopefully I can get a single management console that does the backup independent of the operating system using the extended copy technique," he says.

This feature removes the server from the data path, eliminating the need to copy data to and from host memory, as well as reducing CPU overhead.

The LAN-free vendors - IBM, Veritas and Legato - also have serverless back-up capability. In addition, CA will add serverless back-up features to its SAN integrated Technology Initiative storage network software this year.

In spite of users' enthusiasm for backup that frees up network and server traffic, Lopez says all the pieces are not here yet. Lopez implemented a SAN almost two years ago for Sun and Windows NT, and is still waiting for everything to come together. "Only now are the products coming forth that will let us do serverless backup. SAN technology was a godsend for all my storage, but I couldn't do backup over it," he says. Software from Veritas and Legato have yet to ship.

"There's no single product that's going to let us do it exactly," Lopez says.

"Certain manufacturers don't let us do an exact data copy from device to device and Fibre Channel switch them. We're right on the edge."

SAN adoption rates are still low, even though it is one of the most hyped technologies ever, says Duplessie. "Users are still waiting for an absolutely compelling reason to make a major infrastructure change."

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