I can only speculate, but maybe they're referring to the same thing Andrew Morton meant when he described ZFS as a rampant layering violation.

ie ZFS isn't just a file system. It's a volume manager, raid and file system rolled into one holistic system vs for example LVM + MD + ext4.

And (again I'm only speculating) in their micro kernel design want to have individual components running separately to layer together a complete solution.

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p_l 4 hours ago | parent | next [-]

It's only a rampant layering violation if you mandate the use of external layers like Linux device mapper as the only allowed way... Or you haven't actually read through the code and assume based on external user interface.

No, ZFS is not "monolithic".

It's just that on the outside you have a well integrated user interface that does not expose you to SPA (block layer), ZIO (IO layer, that one is a bit intersectional but still a component others call), DMU (object storage), and finally ZVOL (block storage emulated over DMU) and ZPL (POSIX-compatible filesystem on top of DMU) or Lustre-ZFS (Lustre metadata and object stores implented on top of DMU). There are also a few utility components that are effectively libraries (AVL trees, key-value data serialization library, etc)

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panick21_ 4 hours ago | parent [-]

In the Linux world you need to be hard to use in order to prove how pure you are. Anything that is actually easy to use is always considered unpure and bad.

	▲	creshal 3 hours ago \| parent [-]
		Not sure why you're getting downvoted, considering how people torture themselves with calculating SSD cache sector offsets by hand so they can imitate 1% of ZFS's feature set with LVM2.

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boxed 19 minutes ago | parent | prev [-]

> when he described ZFS as a rampant layering violation

I read some blog posts back in the day about why they did this and it sounded a lot like those layers were more historical accidents or something.

You can turn it around and say that ZFS is a full stack filesystem (or vertically integrated if you will) and it should be pretty obvious that a rethink on that level can have big advantages.