On Sep 13, 2007 00:53 +0200, Filip Sneppe wrote: > Suppose one has an ext3 filesystem on a SAN LUN. > I would like to know if it is possible to freeze this ext3 filesystem > into something > consistent from a filesystem point of view, then trigger the SAN's snapshotting > functionality, and then thaw the ext3 filesystem to resume I/O. This > would allow > near-instantaneous snapshot backups without having to use LVM or > LVM snapshots. You could probably make an ioctl to ext3 to do this, calling the existing code to flush the journal during snapshots. > So, my questions are: > - Is this currently possible from userspace with ext3 ? If not, is this > hard to write ? (I am not an expert programmer, but from looking at the > XFS and GFS userspace code, things are done totally differently) > - Given that all Linux FS support suspending of I/O operations, > is it technically possible to write a generic userspace tool to do just > that: freezing/thawing I/O requests to a mountpoint from userspace, > no matter what the underlying FS is ? Yes, if there is a common ioctl or syscall - the filesystems themselves have a common method to do the freeze/thaw. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc. _______________________________________________ Ext3-users mailing list Ext3-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/ext3-users
