Cloning Data for Disaster Recovery

Companies are scrambling to marry their storage and disaster recovery strategies via data replication.

By Mark Leon

Computerworld |

Even before the Sept. 11, 2001, terrorist attacks and the temporary shutdown of the nation's airlines, IT managers were beginning to use the words disaster recovery and storage in the same sentence, especially in the financial services industry.

But afterwards, the marriage of the two disciplines seemed even more urgent. The potential for disasters seemed bigger, and disaster recovery plans that called for flying tapes across the country seemed naive.

The result is that the words disaster recovery are now actually driving many storage technology projects, as corporate IT managers look for ways to replicate data and send it to sites that are 10, 20 or even hundreds of miles from headquarters. Here are three technology strategies they're using.

1. The Storage Subsystems Approach

When Lajuana Earwood began looking for a new disaster recovery system, she found she was alone. "No one else had done what we were trying to do - we wanted to mirror massive amounts of data over a very long distance, about 700 miles," she says.

Earwood, director of mainframe systems at Norfolk Southern Railway Co. in Norfolk, Va., realized in January 2001 that the company's business systems were too vulnerable. "At the time we were replicating a small subset of our data in real time," says Earwood. "But it was not really enough to carry us through in the event of a major disaster."

The data sets amounted to about 6TB of critical railroad, payroll and order entry information on two IBM mainframes - essentially the railroad's IT hub. So Earwood sent out a bid request to all the major storage vendors; Hitachi Data Systems Corp. in Santa Clara, Calif., got the job in February 2001. "IBM's proposal would have required too much additional hardware," says Earwood. "EMC's solution gave only snapshots. HDS gave us the closest thing to real-time mirroring, and it required less hardware."

And she liked the price. By January 2002, the new system was good to go.

Along the way there was one major change in direction, though. The original plan was to replicate to a site in North Bergen, N.J., about 700 miles away. "But after Sept. 11, we realized that might not be such a good idea. The logistics of transporting personnel could effectively negate all our other efforts," Earwood says. So Norfolk Southern decided instead to use a much closer backup center in Buckhead, Ga., for the mirrored mainframe data.

The sheer volume of data presented another challenge. "We wanted to put all our data in one consistency group," says Earwood. A consistency group is a set of data that is shared by a number of critical applications, but in Norfolk's case all of the data is shared by all of the applications. It made sense on paper, but the execution pushed the technology envelope a bit too far.

"We are using HDS 9960 storage hardware, the HDS TrueCopy replication software and two OC3 network pipes," says Earwood. "It all worked, but we kept hitting the ceiling on high-volume write transactions."

The solution was to split the data into three consistency groups. But Earwood isn't giving up on the original goal. "We are looking at new hardware from HDS that can handle more volumes. This might allow us to consolidate all our data back to one consistency group," she says.

Earwood tests the system with a simulated disaster recovery almost every week. "We are almost down to a four-hour recovery time," she says, "and we now feel that we can go to our board of directors and say that we have confidence in our disaster recovery system."

2. Host-based Software

When Chadd Warwick, operations manager at Comprehensive Software Systems Inc., a financial software development house in Golden, Colo., went shopping for a new business continuity system, he wanted something a little more flexible than the hardware-based systems from vendors such as Hitachi and Hopkinton, Mass.-based EMC Corp.

He found it in Veritas Volume Replicator (VVR) software from Veritas Software Corp. in Mountain View, Calif. "We liked VVR," says Warwick, "because it is a host-based, software solution."

Because the software runs on the server instead of on the disk array, it's independent of the storage hardware. "It meant we didn't have to forklift a new hardware infrastructure in, which meant lots of savings for us," says Warwick.

Warwick started using VVR in November 2001 as a beta tester and decided to stick with it. "This is block-level data replication so the software doesn't need to know anything about the applications or the data. And the hardware independence is really nice," he says. "You can actually restore to different hardware, so, in the event of a major disaster, we could even run down to Best Buy and pick up whatever machines we could find to get us up and running quickly."

Another advantage, Warwick says, is the absence of complex, proprietary network protocols. "VVR uses standard IP," he says. Currently, the company replicates about 400MB to 1GB of data per day - over T1 and T3 lines - from the data center in Golden to a site in downtown Denver.

The software approach is usually cheaper than subsystems products, especially for replication over long distances, says Bob Guilbert, vice president of NSI Software Inc. in Hoboken, N.J., which competes with Veritas. "The subsystems products typically require dedicated fiber, and that can get very expensive."

3. The Hybrid: SAN Over IP

Shimon Wiener, like many of his peers, started looking for a better way to protect his firm's data after the terrorist attacks of Sept. 11, 2001. Wiener is the manager of the Internet and networking department at Mivtachim, a leading provider of pension insurance in Ramat Gan, Israel. It's a part of the world where, unfortunately, disasters aren't a rare occurrence.

The firm has two data centers: one with 600MB, in Ramat-Gan, and the other with 400MB, about seven miles away in Tel Aviv. "We wanted to do a double replication," says Wiener, "so if Tel Aviv goes down, Ramat Gan can take over, and vice versa." But when Wiener went shopping, he was dismayed at the high prices. "We first looked at Compaq, IBM and EMC. None of them could do this without a Fibre Channel connection, which was very expensive," he says.

Wiener finally found what he wanted from Dot Hill Systems Corp. in Carlsbad, Calif. Mivtachim wanted a storage-area network (SAN) at each site, and Dot Hill's Axis Storage Manager software supports IP replication for SAN-based systems.

Beginning in January, the pension company installed the Dot Hill SANnet 7100 hardware in Ram Gat and a second SANnet 7100 in Tel Aviv, and then started replicating between sites. Testing lasted about four weeks. "Initially, we had some problems getting the two systems synchronized," says Wiener, "but we had good support and now we are very satisfied. We replicate about once a day."

Although Wiener got the system for disaster recovery purposes, he says it had a significant side benefit: "The SAN also centralized our data so backups are much easier to manage."

Leon is a freelance writer in Kilauea, Hawaii.

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