Hi! > NEED - provide way for SAN and hardware raid storage to do > its snapshot/copy function while the system was in-use and > get an image that could mount cleanly. Without freeze, at > a minimum we usually needed filesystem metadata recovery > to run, worst case is completely unusable snapshits :) > > freezefs() is single-level: > > ENOTSUPPOTED - by any other fs > EOK - done > EINPROGRESS > EALREADY > > As implemented, freezefs only ensures the metadata is > consistent so the filesystem copy can mount anywhere. > > This means ONLY SOME metadata (or no metadata) is flushed and > then all metadata updates are stopped. User/kernel writes > to already allocated file pages WILL go to a frozen disk. That's the difference here. They do write file data, and thus avoid mmap()-writes problem. ...and they _still_ provide auto-thaw. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
