> FWIW, NetAPP's WAFL and Sun's ZFS are COW file systems. COW makes > it easy(ier?) to do snapshots.
I (think I) get how a COW approach is supposed to work; when you decide to take a snapshot you throw The Big Switch and from then on all writes to blocks on the "device" in question (where the filesystem data reside) are instead written somewhere else so that the filesystem bits aren't changing underneath you as you copy blocks from that device to archival storage. But how do you guarantee that the filesytem is snapshotted in a consistent state? Are you required to somehow force all pending operations to complete and all files to be closed (or whatever) to quiesce the data? Or am I making more of this than is necessary and it somehow isn't a serious problem? (and yes, I could read about this on my own instead of asking questions in class like this, but I figured others might find this interesting, as well...) _______________________________________________ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/
