Opening Up Clustered File Systems

Open source continues to make inroads into enterprise storage, and its latest route is clustered file systems.

Red Hat and Oracle have both been active in the open source clustered file system space recently.

Oracle recently open-sourced its clustered file system (CFS 2). Red Hat has issued a number of announcements for its Global File System (GFS), which it acquired when it purchased Sistina in 2003 and open-sourced in 2004. HP, EMC, Network Appliance and even Oracle are among those that have been mentioned in Red Hat press releases as vendors that have verified GFS as a supported file system for enterprise storage solutions.

Oracle’s Linux Play

Oracle’s namesake database is of course quite proprietary, even though it runs on open source platforms such as Linux. Oracle’s CFS has won the support of Linux vendor Novell and is distributed with Novell’s SUSE Linux Enterprise Server 9 SP2.

“Our file system is free of charge and free support for customers that have an Oracle license,” said Oracle spokesperson Letty Ledbetter. “We offer this to make it easier on deploying our software on Linux.”

Ledbetter doesn’t necessarily see Red Hat’s GFS as competition for Oracle’s CFS.

“We have to allow other companies to provide their products as they go through the right validation processes, so it is up to the customer to chose,” Ledbetter told Enterprise Storage Forum. “We don’t see other CFSs as competition, but we assume that our solution works well, is well integrated, can provide a very good level of support, and is free on top of it.”

Red Hat’s Robert Kenna, senior product manager for storage, sees Oracle’s support of Red Hat’s GFS as a good thing.

“It matches both company’s themes of ‘open,'” Kenna said. “It allows the customer to choose which solution they prefer. Oracle’s signoff removed a key obstacle to making that choice.”

Proprietary Vendors Push Their File Systems

Rick Strom, director of NAS product marketing for EMC, said EMC has not actually endorsed Red Hat’s GFS, but has “qualified” it on a number of CLARiiON arrays through interoperability testing.

“We really don’t have any plans to integrate that technology in,” Strom said. “From a NAS perspective, we already have our own clustered file system.”

From Strom’s point of view, there really isn’t even that much of a need for clustered file systems on NAS, at least.

“The vast majority of the workloads we deal with don’t even need a SAN file system,” he said. “The NAS protocols work just fine for sharing information.”

Andy Fenselau, Symantec’s Linux product line manager for the Storage and Server Management Group, says the Veritas Storage Foundation Cluster File System is a superior solution to either Oracle CFS or Red Hat’s GFS.

“While both Red Hat and Oracle do offer cluster file system products, their products are not nearly as mature or as integrated as Veritas Cluster File System, nor are they tightly integrated with Clustered Volume Managers,” Fenselau said. “Additionally, most data centers have a diversity of platforms, and IT administrators want consistent tools to use across all platforms.”

The Veritas offering supports Sun Solaris, HP-UX, IBM AIX, Red Hat Enterprise Linux, and Novell SLES, Fenselau said “giving customers a unique ability to manage storage consistently across all platforms.”

Red Hat’s Kenna acknowledges that there are other clustered file system options. However, as companies migrate to Linux, he thinks they won’t want to go to third parties for a file system.

“As people are getting into these larger configurations, they see the value of a clustered file system, and there would have to be a significant value add to going to anyone other than Red Hat if you’re basing it on a Red Hat distribution,” Kenna said.

Chris Wood, CTO of Sun’s Data Management Practice, said Sun is supportive of Red Hat GFS, but he thinks that Sun’s SAM FS and QFS clustered file systems are superior choices for enterprise storage needs.

“The main difference is going to be that SAM FS and QFS are hardened seventh-release proven products with 100 percent full vendor support,” Wood said. “It’s been around for a while and the others [GFS and CFS] are fairly new products and they are going to go through teething pains.”

Storage Market Effect Unclear

Opinions on the effect of open source clustered file systems on the storage market vary widely.

Robert Wipfel, distinguished engineer at Novell, said shared cluster file systems are a necessary foundational component for ensuring Linux success in horizontally scaled commodity server cluster and storage network environments.

“We expect to see more adoption of Linux cluster file systems in Enterprise Linux distributions, especially as iSCSI-based storage networking products are also supported and are gaining broader market acceptance,” Wipfel told Enterprise Storage Forum.

Infotech Research analyst Curtis Gittens is of the opinion that Red Hat GFS and Oracle CFS will have a small impact on the storage market.

“Storage hardware is almost completely commoditized, and this means that storage product differentiation must move up to the application level,” Gittens said. “Consequently, I don’t believe EMC, NetApp and others will base their storage solutions on open source clustered file systems.”

In Gittens’ view, vendors that build their storage applications on an open source clustered file system will restrict their ability to differentiate their storage management applications.

“Historically, we have already seen that other open source enterprise file systems like SGI’s XFS and IBM’s JFS have not been widely adopted in the market,” Gittens said. “Although they are not clustered file systems, their enterprise-level capabilities were shunned by vendors who chose instead to develop their own file systems.”

Heterogeneity, Performance Matter

William Hurley, senior analyst at Data Mobility Group, is more upbeat on GFS’ prospects. He thinks that it will have a long-term positive effective for Linux-oriented software developers. He is also of the opinion that as the market matures, transparency will become increasingly important — but that heterogeneity also matters.

“As the use of clustering and clustering technology through the use of integrated file systems become more understood, the resilience of failover and performance aspects of clusters will begin to dull some of those lower-order distinctions, whether you’d choose a SAM, Oracle, Veritas or even GFS,” Hurley said. “At the top end, it comes down to how transparent the operation of the file system is to the operating system, how easy it is to manage and whether that system will support a certain degree of heterogeneity.”

“We see that GFS right now clearly is an outstanding offering for the Linux-only world, but is distinctly challenged when faced with heterogeneity,” he said.

Heterogeneity is an area where Fenselau says Veritas has an edge, although he does see a role for GFS and CFS.

“These open source file systems are important additions to the overall Linux ecosystem, and they are a great fit for low-end and isolated [non-data center] workloads,” Fenselau said. “However, most enterprise data centers require levels of performance, scalability, integrated and manageable functionality, and non-stop online storage virtualization that none of the open source tools can deliver upon.”

Red Hat’s Kenna notes that GFS has more than 150 customers in three years of commercial deployment.

“This provides comfort and encouragement for new users,” Kenna said. “Plus, we’re actively working to have GFS achieve acceptance upstream.”

Could Sun Be Next?

Red Hat GFS and Oracle CFS could potentially be joined by an open source Sun clustered file system at some point in the future as well.

“I happen to believe in open source, and who knows, we may open source SAM FS and QFS,” Sun’s Wood said. “That’s not a promise, that’s a ‘maybe.'”

Wood said he thinks the open sourcing of Oracle CFS and Red Hat GFS will be an overall positive.

“It lends credibility to the entire concept of a clustered file system, multiple disparate servers accessing the same data, which has been fairly esoteric until now,” Wood said. “It has typically lived in the more technical computing space. This kind of brings it into the mainstream. I expect to actually see an increase in interest now that this stuff has been open sourced. I think you’ll see a lot of innovation and innovative uses.”

Jeffrey Wade, HP’s worldwide Linux marketing manager, said it’s too soon to tell what affect open source clustered file systems will have on enterprise storage, but sees the development as a positive one.

“It is very exciting to see such sophisticated technology made available as open source,” Wade said. “As the market has shown, more and more customers are looking to leverage open source software to address increasingly complex business needs, and storage certainly is a vital component of the overall solution.”

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