17 Facts About ZFS

ZFS is a file system with volume management capabilities.

In 2013, OpenZFS was founded to coordinate the development of open source ZFS.

ZFS is unusual because, unlike most other storage systems, it unifies both of these roles and acts as both the volume manager and the file system.

ZFS includes a mechanism for dataset and pool-level snapshots and replication, including snapshot cloning which is described by the FreeBSD documentation as one of its "most powerful features", having features that "even other file systems with snapshot functionality lack".

ZFS was designed and implemented by a team at Sun led by Jeff Bonwick, Bill Moore and Matthew Ahrens.

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ZFS was ported to Linux, Mac OS X and FreeBSD, under this open source license.

In September 2007, NetApp sued Sun claiming that ZFS infringed some of NetApp's patents on Write Anywhere File Layout.

Consistency of data held in memory, such as cached data in the ARC, is not checked by default, as ZFS is expected to run on enterprise-quality hardware with error correcting RAM, but the capability to check in-memory data exists and can be enabled using "debug flags".

ZFS to be able to guarantee data integrity, it needs multiple copies of the data, usually spread across multiple disks.

ZFS relies on the disk for an honest view to determine the moment data is confirmed as safely written and it has numerous algorithms designed to optimize its use of caching, cache flushing, and disk handling.

Unlike most other systems where RAID cards or similar hardware can offload resources and processing to enhance performance and reliability, with ZFS it is strongly recommended that these methods not be used as they typically reduce the system's performance and reliability.

The maximum limits of ZFS are designed to be so large that they should never be encountered in practice.

ZFS uses different layers of disk cache to speed up read and write operations.

An advantage of copy-on-write is that, when ZFS writes new data, the blocks containing the old data can be retained, allowing a snapshot version of the file system to be maintained.

ZFS snapshots are consistent, and can be created extremely quickly, since all the data composing the snapshot is already stored, with the entire storage pool often snapshotted several times per hour.

Authors of a 2010 study that examined the ability of file systems to detect and prevent data corruption, with particular focus on ZFS, observed that ZFS itself is effective in detecting and correcting data errors on storage devices, but that it assumes data in RAM is "safe", and not prone to error.

ZFS was widely used within numerous platforms, as well as Solaris.