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HP Open Sources Unix File System for Linux

HP is opening up its Tru64 Advanced File System (AdvFS) to the open source Linux community in a bid to help further Linux file system innovation.

The AdvFS file system, which has its roots in Digital Equipment Corporation's Digital Unix, is used in mission-critical deployments by HP customers. But HP, which gained AdvFS through a series of acquisitions, has its own flavor of Unix, HP-UX, with its own file system.

HP's move to offer AdvFS to the open source community comes as Linux continues moving upstream into deeper mission-critical deployments -- where users often expect certain types of Unix functionality that has yet to become available in mainstream Linux file systems.

"In looking at the ways we could help the Linux community make further progress we recognized that many of the features on the desired list for developing a next generation file system are in AdvFS already," Bdale Garbee, CTO for HP's open source and Linux organization, told InternetNews.com.

While it's open sourcing AdvFS, HP's goal specifically expecting to see the Unix file system ported to Linux users.

"Honestly, our expectation is that AdvFS itself won't necessarily be a focal point for development," Garbee said. "Rather, this will be a codebase that is seen as a treasure trove of algorithms and example implementations from which Linux developers can extract the jewels to incorporate into other file systems."

Some of those jewels that Garbee hopes Linux developers adopt are capabilities like backups and routine administrative tasks, such as resizing volume sizes.

"The enterprise expectation is that you can do those tasks with the file system remaining online, and that's not currently part of mainstream default file system capabilities on Linux," Garbee said.

"From our perspective, the timing is driven by a convergence of our interests in advancing Linux for use by enterprise customers," Garbee added. "At the same time ... the Linux kernel community and file system developers are realizing what they need to do and changes that may need to be made to deliver more capabilities to customers."

For the past 16 years, the Tru64 AdvFS file system has been shipping to DEC, and later, Compaq and HP customers -- Compaq bought out DEC in 1998, while HP merged with Compaq in a deal finalized in 2002.

Buying Compaq and AdvFS gave HP control over a second file system that differed significantly from the system used in its HP-UX Unix operating system.

Garbee said that while efforts had been underway to port AdvFS's features to HP-UX, the initiative was scrapped to enable HP to focus on the Compaq transaction.

In 2004, the company dropped its previous plans of integrating the two systems entirely, instead opting to use Veritas's file system and volume management technology to speed up deployment of similar features on HP-UX.

AdvFS development and support has continued at HP for Tru64 customers, however.

Unix file systems going open source is not a new thing. However, Garbee said HP's approach, which lets developers pick and choose the features they want to integrate into their own projects, is a way of open sourcing a file system that coincides with the way that Linux itself works.

HP uses the GPLv2 license for AdvFS, which also serves to differentiate it from other open source Unix file systems, notably Sun's ZFS.

"Sun's ZFS is very interesting and very competent, but unfortunately as they did with the Solaris community, they chose to release under CDDL," Garbee said, referring to the open source Common Development and Distribution License. "CDDL is a reasonable license, but it is incompatible with GPLv2, which is the license of the Linux kernel. So while ZFS is technically interesting, its choice of licensing makes it not relevant to Linux developers."

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