VMware takes on data migration

VMware supports migrating data between disk arrays with Storage VMotion, changing the equation between server and storage virtualization devices.

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The newest release of VMware, announced this week, includes a data migration capability that users have wanted for years, one that analysts say should prompt storage vendors to change the way they approach server virtualization.

The Storage VMotion feature in the next revision of the VMware Infrastructure due later this year will let users migrate data associated with virtual machines on shared storage systems the same way that VMware's VMotion allows the migration of servers.

Users began emphasizing the need for a storage version of VMotion as early as last May's Storage Decisions conference in Chicago, where several attendees said that having to reboot virtual machines when migrating data between arrays caused frustrating downtime.

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Storage VMotion users will be able to run an internal VMware utility during storage array refreshes or for load balancing on existing arrays. The utility sprang out of a script briefly provided to users when VMware introduced VMware Infrastructure 3 (VI3) in its last major refresh in June. VI3 required the migration of data from the old version of VMware's file system to a newer one.

Storage VMotion requires the use of a command-line interface (CLI) to initiate data migration jobs in the first release, according to Jon Bock, senior manager of product marketing for VMware. After users enter the data to be migrated, its location and destination through the CLI, the migration job can be tracked through VMware's GUI, Virtual Center, according to Bock.

"It was a matter of prioritizing time to market on certain features as part of a much larger major release," Bock said of the decision not to integrate Storage VMotion with Virtual Center. "Users indicated that even a command-line version would solve enough problems for them that they'd rather not wait."

In certain cases, this new capability in VMware has users rethinking the purchase of storage virtualization products, which, until this release, had been the only alternative for migrating virtual machine data without disruption.

"I try to avoid storage virtualization appliances if I can," said Tom Becchetti, senior storage engineer for a medical manufacturing company he asked not be named. "Adding another device to my environment goes away from my principle of keeping things as simple as possible." However, Becchetti said he had been considering deploying a virtual appliance solely to move virtual machines between storage subsystems. "It was that much of a hassle," he said. Now, he said, he's relieved to have to avoid opening that can of worms altogether.

Evaluating other storage virtualization products

However, other users said they will still evaluate storage virtualization products for the problems they can address beyond VMware. For example, one Storage VMotion beta tester said his company is still evaluating Hewlett-Packard Co.'s (HP) XP24000 virtual array and IBM's SAN Volume Controller (SVC) for simplifying storage management.

"It would be nice to have something like the XP [array] aggregate and manage all our storage, from both physical and virtual servers, as one pool [which Storage VMotion won't do]," said Jason Lochhead, principal architect for managed hosting provider Terremark Worldwide Inc.

Storage VMotion also does not address a mix of data from physical and virtual environments, Lochhead pointed out. Users will still need a separate tool to migrate any data not associated with VMware's VMFS file system, which also includes data VMware uses on "raw" block-access devices.

Data migration is still the leading consideration reported by users who buy storage virtualization products, according to recent research from both the Taneja Group and TheInfoPro. Still, other analysts pointed out that hosts won't have the horsepower to do wholesale migrations from one array to another in large environments.

"VMware isn't going to deal with the universe," said Tony Asaro, senior analyst with the Enterprise Strategy Group. Big shops are also more likely than smaller ones to have servers that don't run on the x86 platform, which is currently the only type VMware supports.

Despite the limitations of Storage VMotion, VMware's influence has been creeping into the storage world, according to the Taneja Group's Arun Taneja. "Storage VMotion doesn't do everything storage virtualization devices can do, such as allowing two storage devices to look like one," he said. "But this needs to be a warning shot to the storage industry. The boundaries are shifting. There's going to be a major transformation in the way servers and storage work together over the next two to three years."

"If I were IBM or Hitachi, I'd figure out how best to integrate my product with Storage VMotion," Asaro said, suggesting the "horsepower" issue for large-scale migrations is the likeliest place for storage virtualization devices to get in on Storage VMotion. "You need that big engine for tons and tons of data."

Large-scale data migration

VMware's Bock confirmed that integration with storage virtualization devices for large-scale data migration is being considered as part of the recently announced Storage Virtualization Certification program. "We are talking about how to better leverage [storage system] tools, even existing block copy tools," he said. "Using Storage VMotion to migrate metadata and storage virtualization tools to migrate the bulk of the data in the background, it's definitely a conversation we've had."

According to Bock, another project being considered by VMware and its partners in replication and storage virtualization is VMotion over geographic distances. Users are beginning to clamor for it also. "We do have a number of customers requesting it," Bock said. "We want to understand what the actual needs are and which features are best to implement within VMware or on the storage side."

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