On 13/03/2008, Daniel Phillips <phillips@xxxxxxxxx> wrote: > Hi Duane, > > Thanks for doing this. Some perhaps not so obvious fallout from the bad > old way of doing things is that ddnap (zumastor) hits an issue in > replication. Since ddsnap allows journal replay on the downstream > server and also needs to have an unaltered snapshot to apply deltas > against, if we do not take special care, Ext3 will come along and > modify the downstream snapshot even when told not to. Our solution: > take two snapshots per replication cycle (pretty cheap) so that one can > be clean and the other can be stepped on at will by the journal replay. > Ugh. Ah, good to know, thanks. It looks like you folks are doing some interesting things there. > With your hack, we can eventually drop the double snapshot, provided no > other filesystem is similarly badly behaved. Excellent, I'm really pleased to hear that. > Re your page translation table: we already have a page translation > table, it is called the page cache. If you could figure out which file > (or metadata) each journal block belongs to, you could just load the > page table pages back in and presto, done. No need to replay the > journal at all, you are already back to journal+disk = consistent > state. Hmm, interesting. I'll have to have a think about that, thanks. > mapping. As it stands your solution seems well built, after a quick > readthrough. Nice looking code. I think you added about 250 lines > overall, so tight too. Thanks again. Thanks very much, I appreciate it! Cheers, Duane. -- "I never could learn to drink that blood and call it wine" - Bob Dylan -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
