Please let me know if I'm getting off topic for the ext4-devel list. My point is not to advocate ZFS over ext3/4 since ZFS still has its share of issues. No resizing raidz vdevs, for example, and performance in certain areas. My only point is to make it clear that ZFS on Linux is available (and not necessarily a bad choice) to people reading the ext4-devel mailing list looking for ZFS-like features like the original poster. On Mon, 2008-07-28 at 08:40 -0400, Theodore Tso wrote: > On Sun, Jul 27, 2008 at 10:15:59PM -0600, Eric Anopolsky wrote: > > It's true that ZFS on FUSE performance isn't all it could be right now. > > However, ZFS on FUSE is currently not taking advantage of mechanisms > > FUSE provides to improve performance. For an example of what can be > > achieved, check out http://www.ntfs-3g.org/performance.html . > > Yes... and take a look at the metadata operations numbers. FUSE can > do things to accellerate bulk read/write, but metadata-intensive > operations will (I suspect) always be slow. It doesn't seem too much worse than the other non-ext3 filesystems in the comparison. I'm sure everyone would prefer a non-FUSE implementation and the licensing issues aren't going to go away, but this post on Jeff Bonwick's blog gives some hope: http://blogs.sun.com/bonwick/entry/casablanca . Even so, not everyone needs a whole lot of speed in the metadata operations area. > I also question whether > the FUSE implementation will have the safety that has always been the > Raison d'être of ZFS. Have you or the ZFS/FUSE developers done tests > where you are writing to the filesystem, and then someone pulls the > plug on the fileserver while ZFS is writing? Does the filesystem > recovery cleanly from such a scenario? I haven't personally tried pulling the plug, but I've tried holding down the power button on my laptop until it powers off. Everything works fine and scrubs (the closest ZFS gets to fsck) don't report any checksum errors. The filesystem driver updates the on-disk filesystem atomically every five seconds (less time in special circumstances) so there's never any point at which the filesystem would need recovery. The next time the filesystem is mounted the system sees the state the filesystem was in up to five seconds before the power went out. The FUSEness of the filesystem driver doesn't seem to affect this. Cheers, Eric
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