On Thu, 28 Feb 2008, Uwe Dippel wrote: > > 1. The application (NFS - sftp) does not know about the state of writing?
Sometimes applications know about the state of writing and sometimes they do not. Sometimes they don't even know they are writing. > 2. Obviously nobody sees anything in having access to all versions of a file > stored there? First it is necessary to determine what "version" means when it comes to a file. At the application level, the system presents a different view than what is actually stored on disk since the system uses several levels of write caching to improve performance. The only time that these should necessarily be the same is if the application uses a file descriptor to access the file (no memory mapping) and invokes fsync(). If memory mapping is used, the equivalent is msync() with the MS_SYNC option. Using fsync() or msync(MS_SYNC) blocks the application until the I/O is done. If a file is updated via memory mapping, then the data sent to the underlying file is based on the system's virtual memory system so the actually data sent to disk may not be coherent at all. Bob ====================================== Bob Friesenhahn [EMAIL PROTECTED], http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
