See this link . Not good for ZFS.
A day after someone posted an amusing and somewhat contradictory set of reasons why they preferred Sun x4500 to JackRabbit (including the “if a RAID card fails you have to replace it, and this is bad” in close temporal proximity to “the SATA controller failed and we had to replace the motherboard”, with the first offered up as to why JackRabbit was not as good as x4500, and the second as to why x4500 was better … you can read this amusing gem on the beowulf list if you wish …) we see ZFS being attacked on patent grounds.
There is lots of hype, and this is the right word, around ZFS. It could be a good file system. As Linus and others have noted, it is, by design, a massive layering violation: it has operation and impact across layers that should be independent. Without that independence, a failure in one of the layers might not be localizable to that layer, and have impacts up and down the stack. This isn’t a minor caveat, think of a GUI which writes low level bytes to a disk. That would be a layering violation as well, and just as egregious.
ZFS has captured significant interest (in part due to Sun’s massive over-hyping of it). It combines low level disk block managers with volume management with file systems. It claims it is the first to do this, though if you look at the documents (man pages) for xfs, you realize that xfs had hooks for this (without the layering violations) long long ago on IRIX. That said, I don’t remember using this “feature” under Irix at all.
ZFS’s big claim to fame from an admin’s point of view is that building file systems across lots of disks is easy. From a safety point of view, it calculates checksums on more things than most file systems. This is not a bad thing BTW.
The latter issue is a good one, and all file systems should emulate that. The former is automatable using good tools. OpenFiler does this with a GUI for example. EVMS2 does this very nicely as well. That is, ZFS does what other tools do, and I am sure others will complain that Sun has something really novel here (I am not quite sure I agree).
The interesting parts of ZFS have more to do with data safety than anything else. But now its future may be in question as it appears to have tramped all over WAFL from NetApp. That was not a good move.
Hopefully we will be able to separate the hype from the reality, and play with ZFS on Linux soon, compare it to xfs and jfs. But the patent bit looks like it might put that on hold for a while.