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Home > Like a DNS server, file virtualization saves time for storage admins |
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That global namespace eliminates the need for discrete drive mappings and mount points to connect the clients with the file servers and storage devices. Instead, requests go to the virtual representation of those file systems -- the global namespace -- which routes the calls to the proper server. If namespaces were the only truly benecial features in file virtualization products, storage managers might simply opt for the built-in DFS technologies that ship with Microsoft Windows Server. DFS allow administrators to group shared folders on different servers into one or more logically structured namespaces and synchronize folders between the servers. Administrators of Unix- or Linux-based environments can use automounters to access files through the NFS protocol.
Moving file in the background Another scenario where file virtualization products are helpful is managing policies to utilize storage more efficiently and cost-effectively. For example, an administrator might want to shift files that haven't been used for 60 days to cheaper storage devices or different servers. "File virtualization is about creating that logical abstraction layer between the client and the file and where it's stored, but that's just step one," said Scott Shimomura, a product marketing manager at Brocade Communications. "The real reason that IT wants to virtualize the files is to simplify management of files and file resources." Products that can help users reap the meatier benefits of file virtualization include the Windows-focused StorageX software add-on from Brocade and appliances such as Rainfinity from EMC, the Acopia ARX Series from F5 Networks, Maestro File Manager from Attune Systems and Brocade's File Management Engine. But before selecting a file virtualization product, storage managers need to weigh the built-in operating system services versus the software-only and appliance-based options, as well as whether the product employs an in-band or out-of-band architectural approach. Microsoft noted that its DFS namespaces and replication technologies come at no additional cost with Windows Server 2008. Third-party appliances can range from $15,000 to $180,000 apiece. But Kevin Yam, technical product manager in Microsoft's Windows storage solutions division, acknowledged that DFS may require additional hardware to meet performance and scalability requirements in large deployments and does not offer the file-level granularity that some appliances do.
In-band approach "We decided upfront that we were going to be in-band because we felt that's where a lot of the business value was," said Nigel Burmeister, Acopia's director of product marketing. "The challenge is it's much more difficult to build. The actual implementation of this approach is a purpose-built switch. It's not a PC off the shelf. That would have a tough time scaling to multiple custom-built NAS heads." One criticism of the in-band appliance approach is its potential to create a single point of failure or bottleneck directly between the clients who need to access the files, and the servers and devices that store the files on the back end. Crump, however, dismissed that criticism as "a bit weak," saying, "Most of these systems are sold in highly redundant scenarios where there's at least two boxes at a minimum and, many times, those boxes are also replicated." "Can you put so much data into the box that the box actually ends up being the hindrance to performance?" Crump asked. "What we've seen in actuality in our testing is that it's virtually impossible to plug these boxes. If you right-size the box for your environment, it's very unlikely that a group of Windows users could saturate one of these boxes because the receiving client is relatively slow in and of itself." But Eric Kaplan, director of marketing for EMC's Rainfinity appliance, said that many of the company's customers have more than 50,000 users and hundreds of terabytes of data. He maintained that Rainfinity's hybrid approach -- in-band when necessary and out-of-band the rest of the time -- is more scalable. "The benefit of our approach is that at all times clients are still mounted to the original file servers, so there's no disruptive mount and remount to put Rainfinity in place," Kaplan said. "When we do have to move data around, we're not in front of all of your file servers. We are basically getting in front of, or in-band, for only the segment of data that we're moving, and all of your native file server functionality still works as advertised by the vendor." In out-of-band mode, client machines access a reference server that tells them where the data they want is stored, cache that information and then connect directly to the file server or NAS device to access the data. But the out-of-band approach has two main disadvantages: Administrators can't do live data migrations, and some products may require the installation of software agents. About the author: Carol Sliwa is a veteran IT journalist. Go back to the beginning of the File Virtualization Special Report.
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