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The object debate
Paul Carpentier, Caringo's CTO and co-founder, invented CAS as founder of FilePool, which became Centera after it was sold to EMC in 2001. Carpentier has become perhaps the most outspoken proponent of object-based storage systems as a replacement for file systems altogether. "It's a heated debate," Carpentier said. "Personally, I'm very convinced we've stretched the hierarchical thing way too long."
Carpentier argues that file systems were originally built to allow concurrent access to smaller groups of objects shared among a few users. But now, he said, there's a "mismatch between prevailing use cases [for unstructured data] and how those systems work. Ninety percent to 95% of us don't need a storage system with concurrent locking for reference information."
Carpentier noted that the management of file systems is too meticulous to be practical at petabyte scale. "Some products create a virtualization layer that presents a global namespace, but there might be 20 underlying file systems you have to manage individually, and sooner or later the Web 2.0 business model bumps into an impossibility," he said. Furthermore, at scale, "backup just doesn't cut it anymore, you need live replication."
Object interfaces decouple data from the underlying disk hardware in a way file systems can't keep up with, said Cleversafe CEO Chris Gladwin. "With objects, there isn't a size limit or a concept of drive size; there's just
One EMC and NetApp user said he agrees with this point of view. "I feel really strongly that the file systems we have today are not all that great. In the mainframe days, you could include attributes with a file to help manage them," said Tom Becchetti, a veteran storage professional who asked that his company not be named because of organizational policy. "With file systems, if you need to manage some files differently from others, you do it in separate server buckets today."
That runs counter to the consolidation going on with server virtualization, and Becchetti said object-based storage "could be a key enabler to grow the virtual [server] world, where an object isn't a file but a VMDK [virtual machine disk file]. It could mean I could share a VMDK between more physical servers than is possible with today's file systems, and protect it on a grander scale with policy-based management, where I could say anything with 'P' in the VMDK name should be protected this way vs. anything with 'D' in the name."
Still, even in some of the most demanding environments, users said file systems can get the job done. Speaking on a recent Wikibon.org conference call, Eugene Hacopians, senior system engineer at The California Institute of Technology (the academic home of NASA's Jet Propulsion Laboratory), said the 2 PB of storage in his environment, comprising billions of 5 KB to 25 KB files, still runs mostly on traditional storage systems from Nexsan Technologies Inc.
But that's been a matter of timing, project lifecycles and budget rather than technical preference. "We have looked at [object-based storage] and are considering it for newer projects," Hacopians said. "It's difficult to convert to new technology and fork out additional money when you're in the middle of trying to deliver on a project."
This was first published in December 2009