Switching storage vendors


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Five ways to move data across storage platforms

Network Appliance to EMC Symmetrix
Fast-growing Overstock.com, an online merchandise discounter in Salt Lake City, deploys multiple clusters of Dell servers running Linux and an Oracle database. Since September 2004, it has been moving clusters of servers as quickly as it can from a Network Appliance (NetApp)

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platform to its new 70TB Symmetrix. Overstock.com felt forced to undertake the forklift upgrade for two reasons: The NetApp filers couldn't handle the workload, and it was unhappy with vendor support.

For Overstock.com, the trick was moving to the new storage while maintaining 24x7 operations. The Web site is taken down only once a year, says Shawn Schwegman, Overstock.com's VP of technology, and the biggest challenge was moving the Oracle database.

"We installed Oracle on a new cluster of servers connected to the EMC. We then exported the data from the old cluster to the new cluster using Oracle's hot standby capability. Then, we restored the cluster on the new database," says Schwegman. The migration team then spent the next few hours copying transaction logs to the new database cluster. "From the database perspective, this is the easiest way--the way Oracle recommends," he says.

An alternative approach is to shut down the database entirely, back it up all at once and then restore it on the new platform. "If you have a smaller database, this works well," says Schwegman. Overstock.com's problem was its multiterabyte database, which would require more than a day to copy the logs over the network. Overstock.com tried the recommended standby database approach in a test environment and found that it took only four to six hours to bring up the standby database.

Having resolved how to move the critical database cluster by cluster, Overstock.com was then comfortable letting EMC direct the rest of the migration and configuration. EMC analyzed the storage on the NetApp box, which revealed hot spots among the LUNs. Based on this, it recommended distributing the database differently.

"We spread those LUNs over more disks because certain tables were getting hit too much," says Schwegman. Overstock.com also accepted the EMC read-ahead cache algorithm, which delivered better than a 99% cache hit ratio, higher than it achieved with NetApp.

EMC also helped set up the zones and masking. "Usually, we'd never allow a vendor to do this, but our people were looking over [EMC's] shoulders all the time. Now our people are trained and we can do this [process] ourselves," Schwegman says.

As clusters moved from the NetApp platform to new clusters connected to the EMC platform, Overstock.com wiped clean the servers previously connected to NetApp, swapped out the network cards for SAN cards and put the servers back in service. "We've got it pretty well scripted and documented," says Schwegman. The company can now turn over a six-node cluster in a day.

EMC to BlueArc NAS
After repeated attempts by EMC to fix its aging storage array proved unsuccessful, Mark Chandler, director of information systems at Cambridge, MA-based NeoGenesis Pharmaceuticals Inc., decided to switch storage platforms. The first crisis was what to do with the company's incessant data stream coming from its lab instruments while its primary storage was down. "We were juggling for a week, putting the data on different servers, wherever we had space," he says. At one point, NeoGenesis stopped collecting new data and worked only with what it had.

The second crisis was moving the data from the EMC box to its initial 2TB of new BlueArc Corp. NAS storage. "The EMC [array] had locked itself up trying to recover, so we couldn't get at that data," Chandler explains. Instead, the company reverted to older tape backups, recalled from an offsite archive facility, and restored the data directly onto the new NAS box. NeoGenesis used a 25-tape LTO backup system.

Configuring the new NAS device wasn't a problem due to upfront preparation. Chandler's team spent considerable time planning the details of how the raw storage space was to be configured. The configuration they decided on was then built at the factory. "When it arrived, we put FC on the back and the control head saw the storage right away," he says.

Redirecting NeoGenesis' devices and servers to the new storage was straightforward. "BlueArc looks like a standard network file system share. It registers itself in Active Directory like any other server," says Chandler. And because the company runs CIFS and Unix shares, all NeoGenesis needed to do was modify two lines of code and everything went where it was supposed to go.

Changing storage platforms is getting easier. With planning and help from the new vendor and consultants, a platform change can be manageable. Although it's not yet as intuitive as loading songs onto an iPod, switching vendors isn't the hassle it once was.

This was first published in July 2005

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