What Linus Torvalds Gets Wrong About ZFS

Ars Technica recently ran a rebuttal by author, podcaster, coder, and “mercenary sysadmin” Jim Salter to some comments Linus Torvalds made last week about ZFS.

While its reasonable for Torvalds to oppose integrating the CDDL-licensed ZFS into the kernel, Salter argues, he believes Torvalds’ characterization of the filesystem was “inaccurate and damaging.”

Torvalds dips into his own impressions of ZFS itself, both as a project and a filesystem. This is where things go badly off the rails, as Torvalds states, “Don’t use ZFS. It’s that simple. It was always more of a buzzword than anything else, I feel… [the] benchmarks I’ve seen do not make ZFS look all that great. And as far as I can tell, it has no real maintenance behind it any more…”

This jaw-dropping statement makes me wonder whether Torvalds has ever actually used or seriously investigated ZFS. Keep in mind, he’s not merely making this statement about ZFS now, he’s making it about ZFS for the last 15 years — and is relegating everything from atomic snapshots to rapid replication to on-disk compression to per-block checksumming to automatic data repair and more to the status of “just buzzwords.”

[The 2,300-word article goes on to describe ZFS features like per-block checksumming, automatic data repair, rapid replication and atomic snapshots — as well as “performance wins” including its Adaptive Replacement caching algorithm and its inline compression (which allows datasets to be live-compressed with algorithms.]

The TL;DR here is that it’s not really accurate to make blanket statements about ZFS performance, absent a very particular, well-understood workload to measure that performance on. But more importantly, quibbling about the fastest possible benchmark rather loses the main point of ZFS. This filesystem is meant to provide an eminently scalable filesystem that’s extremely resistant to data loss; those are points Torvalds notably never so much as touches on….

Meanwhile, OpenZFS is actively consumed, developed, and in some cases commercially supported by organizations ranging from the Lawrence Livermore National Laboratory (where OpenZFS is the underpinning of some of the world’s largest supercomputers) through Datto, Delphix, Joyent, ixSystems, Proxmox, Canonical, and more…

It’s possible to not have a personal need for ZFS. But to write it off as “more of a buzzword than anything else” seems to expose massive ignorance on the subject… Torvalds’ status within the Linux community grants his words an impact that can be entirely out of proportion to Torvalds’ own knowledge of a given topic — and this was clearly one of those topics.

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