OVH offers a patch to migrate data with no down time
The OpenZFS project derived from the ZFS project sponsored by Sun Microsystems (purchased by Oracle in 2009). It is a result of a fork in 2005, supported by an independent community mainly made up of former Sun employees. Other than Netflix, which utilizes OpenZFZ on its Titan (2) platform, there aren't many other major IT players claiming to use OpenZFS, whose reliability is now proven.
Traditional storage vendors offer reliable and robust proprietary solutions, which have an undeniable advantage in reassuring users of the sustainability of their data. “The downside,” explains François, “is the price paid. These types of systems rely on specific hardware, which significantly raises the cost per gigabyte and they’re real black boxes in the sense that it's not possible to know how the code works nor is it possible to modify the code yourself.”
Compatible with standard machines (x86 architecture), OpenZFS drastically reduces the cost of storage. In addition, the code is open so OVH is able to adapt and improve upon it. “Ten years after the launch of the project, OpenZFS has reached its maturity,” continues François. Its data integrity verification system, which prevents silent file corruption, is among the most effective. Moreover, OpenZFS features are very rich: snapshot, hot and cold storage, etc." In 2007, OVH abandoned EXT3 to take advantage of ZFS and took interest in OpenZFS in 2009. The first OVH projects in production under OpenZFS became reality at the end of 2011 and it has now become the underlying technology of many OVH.com services: e-mail, web hosting, VPS Classic, NAS-HA, Dedicated Cloud, Backup Storage, etc. “At the time, the technology was already mature and the expertise we acquired has allowed us to effectively compete with proprietary storage systems.”
This OpenZFS experience is exactly what François and Alexandre went to San Francisco to share.“Our technical presentation covered the subject of data migration under OpenZFS. Our hosting activity requires that we continuously allocate and deallocate storage spaces (zpools), which causes fragmentation issues. For this reason , we must regularly perform data migrations. Unfortunately, due to constraints linked to the use of NFS in our infrastructures, OpenZFS doesn’t allow carrying out operations without downtime. We attempted to solve this problem through trial and error.” The patch written by Alexandre and named “Zmotion”, was reviewed at a community workshop that Matt Ahrens was attending (cofounder of the ZFS project). It was proposed for upstream commitment and is already available on Github. “We think that this is something of interest to large companies because the issue of data migration is a reccurring subject of discussion on the community mailing-list”, explains Alexandre.
Watch the “Live Migration with Zmotion” presentation by OVH: