Rein in NAS with file virtualization


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Moving in-band
Because of user concerns about putting devices in-band, some in-band file virtualization appliances give users the option to first deploy their appliances in an out-of-band configuration. Attune Systems' Maestro File Manager can be operated in three modes: discovery, native and extended. In discovery mode, Maestro File Manager allows users to initially discover, analyze and report on storage usage and utilization on their network file servers without putting it in-band. In that mode, it generates reports on information such as CPU and storage utilization, file-access patterns and throughput on specific network ports. These reports let organizations determine the true benefits they'll realize from deploying file virtualization, and appropriately configure and size the file virtualization appliance.

Another key consideration when selecting and configuring in-band appliances is their hardware configuration. Both Attune Systems' Maestro File Manager and NeoPath Networks' File Director rely on clustered configurations available with server operating systems: Windows in the case of the Attune Systems product and Linux for the NeoPath device. In both cases, they're configured for active-passive failover, although there may be a delay of up to a minute while the passive server takes over for a failing active server.

Enterprise NAS environments with high availability, transaction or throughput requirements may find the latencies associated

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with these in-band configurations unacceptable. Only Acopia Networks' ARX6000 addresses those concerns in its software and hardware. On the software side, the ARX6000 uses a split-path architecture that separates the data and control paths. The split-path architecture allows the ARX6000 to better support high transaction rates by assigning more frequent file operations, such as reads and writes, to the data path while the control path handles the more infrequent file requests, such as create and delete operations on the file server directory.

The ARX6000 also supports an active-active configuration that allows dynamic failover between the two nodes in the cluster. Ibis Consulting found that with the ARX6000, its general file server availability improved because the firm could migrate files from a network file server that needed maintenance to other file servers still in production. "Before we deployed the ARX6000, maintenance outages could run up to a day," says Lennon at Ibis Consulting. "Now outages last at most four hours on a weekend once a quarter."

To support the higher transaction and throughput rates required by most enterprises, Acopia Networks uses proprietary hardware in the ARX6000. Adaptive Services Modules (ASM) speed up the control path functions of directory changes, while Network Services Modules (NSM) accelerate file read and write operations.

But despite the immediate benefits derived from file virtualization appliances, some users are still uncertain about the role file virtualization appliances will play in the long term. Storage architect Peterson only uses EMC's Rainfinity when he needs to perform file migrations within his corporate NAS infrastructure, while the City of Jacksonville's Hayes anticipates removing Attune Systems' Maestro File Manager once he finishes consolidating on a NAS gateway. Given situations like these, vendors are trying to ensure that their file virtualization appliances become more than just one-time file migration tools.

This was first published in March 2007

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