One thing is for sure: ZFS is always changing and improving, and creative new uses pop up all the time. If you're running ZFS on a Thumper or even custom-built servers, you need to keep up with the technological changes to take advantage when important new features surface. Here is a list of five must-have resources in your ZFS knowledge arsenal.
There are two aspects to "keeping up" that top the priority list for ZFS administrators. First, you need to be in the loop with best practices and performance reviews to get the most out of your systems. ZFS performance varies vastly depending on how many disks you have in each virtual device. Knowing the tradeoffs will allow you to build (or rebuild) a storage system that works optimally for the workload. Second, is the need to be informed about new ZFS features so you know when to upgrade. Whether it is a stability fix, or a new feature that you have been waiting for, you will find that ZFS is evolving quickly.
The first must-visit resource is the zfs-discuss list found at the opensolaris.org listserv. Other ZFS mailing lists exist as well. The FreeBSD list, for example, is also quite active.
Mailing lists are great because of the wide audience they reach. They are also great because you can search the archives. Chances are good that any ZFS question you can think of has been answered at least once on a mailing list. Your specific need may not be addressed, but it is common to at least find a bit of information that leads you in the right direction or that helps you form a better question for your own posting to the list.
It may seem strange to cite one person's blog, especially above some of the official documentation listed in the next section. Strange, but true. If you've ever searched for anything related to "how to" do something in ZFS, you've probably read an excellent set of instructions from Ben Rockwood's blog.
He frequently experiments and posts his findings to ZFS mailing lists and his own blog. I highly recommend subscribing to his RSS feed, and keeping up with the posts. They are mostly technical, mostly about Solaris, and lately focused a lot on storage and ZFS. You will also find excellent Veritas VxVM documentation on his site, if you're stuck having to use that still. Most Solaris sysadmins know about Ben's blog; on a personal note, it is required reading for my employees.
Sun Blogs are also a great resource. You will find engineers that work on ZFS talking about their progress, and often openly thinking about how it should evolve. Once you find a kernel engineer's blog, it's easy to find others, as they frequently link to one another.
Solaris Information Center at BigAdmin
At the Solaris Information Center's ZFS pages, you will find a nicely formatted, comprehensive set of ZFS documents. This is a great starting point for discovering more about ZFS, especially if you're in the early decision stages about deploying it. The ZFS learning center contains overviews of how everything works, along with demonstration videos that really drive home the usefulness of ZFS.
On the technical side you will find many useful categories, including Oracle on ZFS, troubleshooting guides, tuning guides, best practice documents--it's all here.
ZFS at OpenSolaris.org
You probably aren't running OpenSolaris in production, but you can still benefit from keeping up with new developments on the OpenSolaris side, as they will trickle down into official Solaris releases. The ZFS OpenSolaris Community is where you will find out what features are in the pipeline, and which are likely to make it into Solaris soon.
You may wish to run an OpenSolaris test environment, especially if you're planning on adopting any new features. You can test and become familiar with these new features so that when the time comes to implement them in Solaris they are old-hat and well understood.
IRC,Google, Social Outreach
This may seem obvious, but it is still all too common for people to sit deliberating a problem in isolation. Reach out to the community! IRC is not old, nor is it only used by viruses. The channels #solaris and #zfs on irc.freenode.net are extremely useful. You will always find someone who understands your problem, and likely has already solved it.
A Google search for ZFS related queries will often lead you to one of the above mentioned resources, especially mailing lists and Ben's Blog. Sometimes, however, you will stumble into a whole new world rich with documentation and the kind of material you were looking for. Then you can start to build your own list.
Social networking, as a technical tool, is growing. Even Facebook has a ZFS community. This is much like using the IRC resource, but not as real-time.
It boils down to knowing multiple ways of getting at information. On one hand you don't want to post questions to mailing lists if the answer has been hashed out many times before. Start with some research, then use public forums to illustrate where the documentation was not clear, or explain why your situation is unique and not covered. Don't be shy about communicating your needs or points of confusion; someone else probably has the same question.