Are ZFS clustered filesystems possible?

Is it possible to create a ZFS cluster? Or would you need to go the seemingly ugly (to me at least) route of ZFS with UFS formatted pools governed by GlusterFS?

The idea is to see if it is possible to expand to Multi-Petabyte distributed store which ZFS should be able to handle without a hiccup.

Any pointers, blogs, posts?

You can cluster ZFS with at least two solutions:

"Clustering is now available not only as a commercial product like the RSF-1 solution from www.high-availability.com but also as a OpenSource solution based on PaceMaker. http://www.clusterlabs.org/wiki/Main_Page"

Why yes, it is possible to build an active/passive ZFS-based cluster using shared DAS and multipath SAS.

Details at: https://github.com/ewwhite/zfs-ha/wiki

The key to this high-availability storage design is a shared SAS-attached storage enclosure, or JBOD. While it's not shared-nothing, this can be a useful way of bringing higher availability to a storage setup that can scale vertically.

To complement the shared JBOD enclosure, we need two servers (head nodes or controllers) to provide client connectivity and compute/RAM resources for the ZFS array.

The servers and JBOD enclosure should be arranged in a SAS cabling ring topology.

This can scale using more enclosures...

Maybe this is of interest to you: Sequoia’s 55PB Lustre+ZFS Filesystem

It is from Lawrence Livermore National Laboratory (LLNL). A native port of ZFS on Linux is in developement at that lab.

Not natively. You could have a true clustered filesystem running on top of a ZFS backing store, though...

However, ZFS high-availability (active-active) clusters are available, but that's not what you meant by your question... Maybe the Nexenta Namespace Clustering feature...