On 6/8/11 10:01 AM, Amir G. wrote: > On Wed, Jun 8, 2011 at 5:41 PM, Eric Sandeen <sandeen@xxxxxxxxxx> wrote: >> On 6/8/11 9:04 AM, Amir G. wrote: >>>> And one last note, I also think that the snapshot format change in the >>>>> future, when we'll have snpashots with 64bit feature compatible seems >>>>> just wrong to me. Adding some features or changing the implementation a >>>>> bit is ok, but format change is different. When the code is upstream and >>>>> stable it is just wrong. >>> What can I say, I understand why it looks bad, but is 64bit code >>> upstream and stable? Hell no! e2fsprogs 64bit is not out yet! >>> There is no reason to call it 'format change'. >>> It's going to be a new format used only for 64bit fs, which are not >>> even out there yet. And when they are finally out there, they won't >>> have >>> snapshots until the new format is implemented. >> >> Well, the on-disk format for 64-bit (48-bit?) ext4 is there & fixed; it's >> just that there is no released userspace which can properly handle it, right? > > I don't know, you tell me. > Are there many users out there using 64bit feature, without the proper > user space tools? No, but that doesn't mean the disk format has to change when the tools come out... I just don't want to confuse "there are no tools" with "the disk format is unstable" - Andreas et. al. have been using that format for years. >> >> I don't anticipate ext4 format changes for >16T, or am I missing something? >> >> -Eric >> > > Argh! I wish I hadn't missed the Monday call (it's > not in a good time for me). > This whole 'format change' has gone out of control > and I find it hard to present my case properly on scattered emails. Sorry; I may have just misunderstood... > The message I am trying to get through is: > There is 32bit snapshot file format, which is implemented and well tested. > There is 64bit snapshot file format, which is not implemented yet, so > 64bit and snapshot feature are mutually exclusive. > If and when 64bit snapshot file format will be implemented, it will be > a new type of extent mapped file (v2) with 48bit logical addresses. > Is this a 'format change'? Call it what you will, but it shouldn't > affect anything on existing structures. It should only affect the > non-existing structure of 64bit snapshot file. > > Does this answer your question? Yes, I guess I had misunderstood your point; I thought you were implying that ext4's format had to change to support 64-bit, so why not change snapshots along with it.... But you're just saying that you wish to push 32-bit snapshots which only work with certain sizes of ext4 filesystems now, and later you will release a new snapshot format which works with the larger filesystems. Right? (I don't actually know if we'll ever have 64-bit ext4, though, there are still so many scaling issues beyond just being able to mkfs, mount, growfs etc ... it's a serious game of catch-up with xfs in that space, IMHO, which has been doing it well for years now...) Still, pushing snapshots upstream which will have an on-disk format more limited than the rest of the filesystem's on-disk format does strike me as suboptimal from a pure technical design POV. What if we proposed, say, xattr code that could only apply xattrs to files located in the first 16T? I don't think it'd be accepted. I understand that you have a history and a format and a business case, but that really should not change whether we do it right the first time, upstream, IMHO... But I'm just the peanut gallery, here.... ;) -Eric > Amir. > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
