Hi, On Wed, Mar 12, 2014 at 9:30 PM, Richard Yao <r...@gentoo.org> wrote: > > On 03/12/2014 08:45 AM, Alex Xu wrote: > > On 12/03/14 03:15 AM, Yuxuan Shui wrote: > >> Hi, > >> > >> I would like to implement cp --reflink support for ZFSOnLinux as my GSoC > >> project. > >> > >> cp --reflink is used to create a COW copy of a file, so the file will not > >> take any disk space if it's not modified. This feature is very useful for > >> cases like storing a lot of almost identical virtual machine images. Also > >> this is a frequently requested feature for ZoL. [1][2][3] > >> > >> Currently only btrfs support this feature, so my goal it to bring it to ZoL > >> as well. > >> > >> I think the only way to do it (without changing too many parts of ZoL) is > >> to use the deduplication feature of zfs. A COW copy could be done by create > >> a new entry in ddt for the old file, and create a new file which points to > >> the ddt entry. > >> > >> Please let me know if this proposal makes sense, and if that's the right > >> way to do it. > >> > >> Thanks. > >> > >> [1]: > >> https://groups.google.com/a/zfsonlinux.org/forum/#!topic/zfs-discuss/mvGB7QEpt3w > >> [2]: https://github.com/zfsonlinux/zfs/issues/405 > >> [3]: https://github.com/zfsonlinux/zfs/issues/1063 > >> > > > > While I can't comment too much on the technical aspects, they seem to be > > relatively sound. > > > > However, there are some issues with the, er... other aspects, for lack > > of better terminology. > > > > 1. This is possibly out of scope as a Gentoo project, since ZOL is not > > really part of Gentoo. If it's not, then you're out of luck, because ZOL > > is not an accepted organization. > > Things that provide us with improvements over what we have are > definitely worth consideration as GSoC projects. However, what is > accepted ultimately depends on not only feedback from a potential > mentor, but also a vote of Gentoo developers.
Maybe I could propose this project to illumos? Since they seems to accept proposal for OpenZFS. > > > 2. This is likely too small to be a GSoC project. Perhaps see [0] for a > > list of example ideas, if only so you can get a grasp on the size of a > > good project. > > > > It does sound like a good idea though, and even if you can't do it as > > part of GSoC, you should pursue it anyways. > > Leaning on my understanding of ZFS internals, I can say that this is > large enough. However, I do not think it will accomplish the desired > result if implemented in the manner suggested. Could you elaborate why this won't work? Thanks. > -- Regards Yuxuan Shui
