OpenZFS RAID-Z Online Expansion Project Announcement

The FreeBSD Foundation is pleased to announce a collaborative project with Delphix to implement one of the most requested ZFS features, to allow RAID-Z pools to be expanded one disk at a time. We’ve combined our resources with iXsystems and Delphix to bring this project to fruition. The RAID-Z Expansion project will allow OpenZFS users to incrementally add storage to their RAID pools, one device at a time. The expansion will happen online, in the background, with zero downtime, and while maintaining the redundancy and reliability of RAID-Z.

“From day one, ZFS has been about combining enterprise functionality with ease of use. This feature furthers that by making ZFS’s enterprise-grade RAID capability even easier to use, especially in smaller deployments, where it’s impractical to add a whole RAID-Z stripe at once,” said Matt Ahrens, one of the original ZFS designers. “On a personal note, after hearing requests for this feature for many years, I’m looking forward to working on this and grateful to the FreeBSD Foundation for making it a priority.”

“The basic ZFS building block is the pool, which is is often built using a RAID-Z volume built from five or more disks. Previously, a RAID-Z user who wanted more storage space had to add an entire new RAID-Z set of disks. This project will allow RAID-Z volumes in a pool to be expanded a single disk at a time. Adding this feature requires a deep knowledge of ZFS internals and significant development and testing time. Thus, its cost and complexity has prevented any single organization from pursuing its development,” adds Kirk McKusick, long-time filesystem developer and FreeBSD Foundation Board Director.

Allan Jude, a core team member at FreeBSD states, “This collaboration between the non-profit FreeBSD Foundation and industry partner Delphix towards the development of new cross-platform features, will benefit all OpenZFS vendors and consumers – showcasing the power of platform neutral open-source projects.”

“We are excited to help sponsor this work. The ability to seamlessly extend a ZFS pool using RAID-Z is a feature which will have immediate benefit to our TrueNAS and FreeNAS users around the world,” adds Kris Moore, Director of Engineering at iXsystems.

Improvements such as this continue to make ZFS on FreeBSD an attractive and powerful platform on which to develop enterprise-grade software for both large and small scale. RAID-Z expansion is expected to become available in FreeBSD 12.0.