Hi everyone, 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. >From googling around, I understand that: - LVM can take consistent snapshots at the FS level, and from posts to LKML, I understand that all Linux filesystems now support suspending I/O activity during these snapshots as a requirement for LVM snapshotting. - XFS has a userspace command "xfs_freeze [-u] mountpoint" which appears to do exactly what I want to achieve with ext3 - GFS has a userspace command "gfs_tool [un]freeze mountpoint" which appears to do the same thing 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 ? >From the various posts with similar questions that pop up on various mailing lists and support forums, it would appear to me that there is some level of interest/demand for this type of feature. Regards, Filip _______________________________________________ Ext3-users mailing list Ext3-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/ext3-users
