Users crack NAS scalability problems

Warner Music Group, Anadarko Petroleum and Ascent Media have implemented different virtualization approaches to solve NAS scalability issues.

The problem: Traditional NAS systems support limited file-system capacity -- 16 TB for Network Appliance Inc. and 2 TB for EMC Corp. This means users end up with tens, hundreds and sometimes thousands of separate file systems, which become a nightmare to manage and navigate around.

A variety of different approaches have emerged to work around this problem, and after months of evaluation, users are starting to sift the wheat from the chaff.

Switch-based virtualization

Warner Music Group, part of Warner Bros. Records Inc. in Burbank, Calif., has 30 TB of data on file servers distributed across its network. Approximately 8 TB of capacity was unusable, as the file space was spread across thousands of different directories. Warner has about 30,000 subdirectories containing all of its barcode data. "We had to rob space from one location and give it to another, but we could never do enough work to balance it out," said Michael Streb, vice president of IT services at Warner Music Group.

The company decided to virtualize this directory structure across four separate Celerra data movers (EMC lingo for file servers). Using eight Acopia Networks' switches, it was able to present the directory as one single file across all four locations. Acopia's ARX1000 and ARX6000 switches link to a local Ethernet switch, and tie together NAS storage devices and file servers to create a unified storage pool.

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The ARX switches serve as in-band Unix/Linux NFS and Microsoft Common Internet File System proxies. They facilitate the exchange of files between client computers and multi-vendor NAS storage devices, which are presented to the client as a single virtualized pool of storage. Warner was able to gain a higher utilization of its storage, perform policy-based security, and data migration and load balancing across the infrastructure. Streb looked at the Andrew File System from Carnegie Mellon University for the same virtualization capability, but ruled this out on account of it being "far too complicated" he said.

He noted one shortcoming with Acopia's approach to file virtualization -- it's "per geography and not global," he said. In other words, users with multiple sites will end up with multiple clustered file systems and will ultimately have to find a way to bridge them together. This isn't a big issue for Warner at this point, although Streb believes Acopia is working on a solution.

Global namespace software

Anadarko Petroleum Corp. in Houston, Texas, has 179 TB of SAN and NAS storage mainly on Network Appliance Inc. filers. It had one share in particular that had to be accessed from everywhere and was causing a lot of pain. "Recovery of this 5.5 TB volume took forever and was impossible to manage," according to Carlos Martinez, systems analyst at Anadarko. He decided to split the share up between two filers and use global namespace virtualization software from NuView Inc. to make the data appear like it was still on one system. "We create one link then click VFM (Virtual File Manager, NetApp's rebranded version of NuView's software), and it creates a path to all the thousands of folders underneath," Martinez said.

Global namespace is a type of meta-directory of NAS namespaces that allows storage administrators to automatically move and manage data across heterogeneous NAS environments as if they were a single filer.

Martinez looked at other alternatives, including switches, but wanted a product that worked well with his NetApp filers. "We didn't like the idea of putting hardware in between our servers and storage. We're running Oracle data warehousing and couldn't afford any kind of bottleneck." Another benefit to VFM was its bit-level replication capability, which enabled Anadarko to replace Veritas Software Inc.'s Storage Replicator that at the time forced users into read-only mode when copying data and would only copy entire files. "Veritas told us we needed to get T1 lines between our sites to speed up the process, but we wouldn't do that for an office of 20 people just to use Veritas," Martinez said. VFM allows Anadarko to replicate only changed data, and it can be running in the background while people are still using the application.

IP-based cluster file system

TV post production company Ascent Media Group, a Liberty Media Company, opted not to try and virtualize a mish-mash of back-end storage and instead bought an IP-based cluster file systems product from Isilon Systems Inc.

"It was impossible to scale with the old system. We would add volumes, but it was a nightmare without a lot of archiving," said Rob Cadzow, senior systems engineer at Ascent Media. Replacing its Unix servers and Ciprico storage with Isilon arrays allowed Ascent to create a single clustered file system and keep the same directory structure across all the systems as it is scales up or down. Isilon will only virtualize Isilon storage, however.

Ascent looked at other approaches, but decided that for the price it had to pay it might as well get some storage as well. "We liked the all-in-one approach," Cadzow said.

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