Case study series: Part 3 of 3—Users embrace D2D

Posted on July 25, 2006

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By Michele Hope

Click to read Part 1 and Part 2 of this series.

—Often touted as a nearline source of affordable disk storage, SATA-based storage subsystems are cropping up at a number of sites as a source for both disk-based backup data and data being migrated "downstream" from primary storage as part of an information lifecycle management (ILM) strategy.

K.C. Tomsheck, senior director of IT operations at Vernon Hills, IL-based reseller CDW, chose to piggy-back a D2D architecture on top of a larger ILM project that now consists of 14 individual SANs on the network, including EMC Clariion CX700s, EMC Celerra, and an EMC Centera archive.

Tomsheck decided that an ILM approach would allow him to ultimately buy less storage over time by better using the storage CDW already had.

Tomsheck and his team needed a disk-based solution that could successfully back up the hundreds of terabytes currently in production. They decided to bring in a few EMC Clariion Disk Libraries (CDLs), a type of virtual tape library (VTL) that uses Legato NetWorker software in conjunction with some large Clariion 700 disk arrays at the back-end. One CDL is used at the Vernon Hills data-center location, with another in use several miles away at a remote disaster-recovery site.

Since CDW represents a number of different storage vendors, it began by checking out each vendor's wares before ultimately settling on the EMC gear for ILM and its disk-based backups. The proof-point for going with EMC, said Tomsheck, came in EMC's commitment to ensure a certain level of system performance.

Tomsheck is pleased with the local backup speeds he's getting from server to CDL—approximately 2.8GB to 3.2GB per minute, as opposed to prior backups to tape that ran 200MB to 300MB per minute. Backups of SQL Server databases also now complete in just one to one-and-a-half hours, as opposed to the previous eight hours.

Instant replays
Another organization that decided to tackle a variety of storage issues, including disk-based backup, within one storage solution is the NYU School of Medicine. According to director of systems Jeff Berliner, avoiding the pain of potential downtime to the school's e-mail server became the impetus behind the school's ultimate move to networked storage in the form of two Compellent Storage Center SAN solutions.

Unfortunately, it took a painful, week-long e-mail outage to first convince the organization that networked storage with disk-based backup and replication was a better way to go. Now, all e-mail data resides on one Compellent SAN at the primary data center. Using Compellent's disk-based snapshot technology, which the vendor calls Data Instant Replay, Berliner and his team have scheduled an "instant replay" of specific production volumes to be taken every 15 minutes.

The instant replays are saved on another volume on the Compellent SAN for two hours before being overwritten by newer instant-replay images. Another instant-replay schedule run nightly in conjunction with the nightly backups to tape the school still performs. The nightly instant replay is then saved for one week before being overwritten.

The Compellent SAN uses a variety of different drive types, including SCSI, Fibre Channel, and nearline "Fibre ATA," the latter of which claims to offer performance characteristics close to Fibre Channel, but at approximately one-third the cost. This mixture works well for Berliner's needs, as it allows him to use the primary SAN and now a second Compellent system, located a few blocks away, to host primary production data as well as performing remote asynchronous replication between the two systems via Compellent's Remote Instant Replay functionality.

Like many users, Berliner recognizes his use of D2D has fundamentally changed the role of tape. "We can now have a fully mirrored copy of our data redundant not just locally but also three to four blocks away," he explains. "This is really where tape comes in now. If any disaster takes out both of these sites, the recovery strategy at that point is to use our off-site tapes to perform a complete data-center recovery."

Michele Hope is a freelance storage writer. She can be reached at mhope@thestoragewriter.com


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