It's been 10 years (31 Oct) since the first ZFS prototype was run inside of Sun Microsystems, 4 years later it was integrated in OpenSolaris and available to everyone to test. I've been using ZFS since 2004 and I must say that while I have always been impressed by ZFS it took until 2010 before the last bits where in place to make it really usable in demanding environments without problems. It takes time for a complex and critical system to grow mature, that's why I think ZFS will be the best option for a few years to come even if other systems could provide the same functionality. Today ZFS is available in both commercial and free operating systems as well as the foundation of several commercial storage products such as the Sun ZFS storage appliance and NexentaStor.
Some of the latest ZFS features are only available in the closed version of ZFS owned by Oracle and distributed with Solaris but the free version is also going forward. It 's being developed by the illumos community with companies such as Nexenta, Joeyent and Delphix. The illumos branch of ZFS is also stable and used by the companies developing it in their own commercial products.
ZFS 10 year anniversary
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ZFS working group
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