Erm, sorry for that bit of a rant. After some fiddling with the hex editor I found out a bit more and am trying to be more specific...
1) How are files laid out on disk, and encapsulated as objects? (Not clear from On Disk Specs or "datastructures_for_single_file.pdf") I guess I don't understand the way they are wrapped as objects on the disk. 2) Are there block groups or an equivalent? 3) Are there extent pointers? I've got a ZFS test image with a large text file (234,179 bytes) that is pleasantly contiguous. I wonder if there are no block groups at all... I can't see quite how it is encapsulated as an object, either, since it is larger than a 128kb block. Any tips for reading re. code files would be appreciated. Regards Mark On Monday 30 July 2007 20:51, Mark Furner (Mark Furner <mark.furner at gmx.net>) may have written: > Hi > > Despite having done the RTFM with a Draft On Disk Specifications document, > I'm still trying to get a picture of how ZFS gets laid out disk. It's > rather too high-level and interested in explaining the abstractions to say > much about where in the FS stuff gets put. The PDF file on data structures > of a single file is a bit more helpful, but still is a bit abstract. What I > want to know is how to reconstruct a ZFS pool from an image file as raw > data, which byte goes where. It looks as if I'll have to write up a > description myself. > > AFAIK, the first 4 MB of a ZFS file system is taken up with 2 vdev labels > and 3.5 MB of unused space for future use. But what happens after that? I > found what looks like the meta object set MOS right after the 4 MB > boundary, and later on what looks like a copy of the MOS. (This alone seems > to contradict the On Disk Specifications). When does the reserved space of > the ZFS partition end and the user data begin? Are there block groups? Is > the user-data also contained within dnodes? The On-Disk Specs explain > znodes for file metadata, and it looks as objects have their own metadata > stored in a dsl_dataset_phys_t structure. Where is the file data? > > Can you point me in the direction of the relevant code passages? Any help > would save time with the hex editor... > > Thanks a lot > > Mark > > On Saturday 28 July 2007 00:35, Matthew Ahrens <Matthew.Ahrens at sun.com> may > > have written: > > Mark Furner wrote: > > > Thanks for the clarification, Darren, and sorry for cross-posting. > > > > > > OK, physical device -> pool -> file-system(s) > > > > > > Some questions: > > > > > > 1) zpool import allows options similar to zfs. Can I set the same or > > > similar read-only (RO) options for the whole pool > > > (noexec,nosuid,noatime,nodevices,ro)? > > > > "zpool import -o ro <pool>" -- see zpool(1m). > > > > --matt > > _______________________________________________ > zfs-code mailing list > zfs-code at opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-code
