> Stefan Raspl [raspl@xxxxxxxxxxxxxxxxxx] wrote: >> If I understand Takahiro correctly, the main issue is that the whole >> log device becomes unusable in case one leg is broken...? Of course, >> we still have the other leg with the most recent data available and >> can read from that one. However, this would require that we can >> start a mirror in rw-mode (so we can keep the still-recent half up >> to date) even if one half has failed - a functionality which was >> recently added to LVM, as we discussed in our last call...? > > Stefan, Takahiro is using the latest LVM that brings LVs in rw-mode. > That is not the problem. Actually, everything works if a slave leg of a > "log mirror" is broken. But if the master leg of the "log mirror" is > broken, entire log device becomes unusable. The reason is when we > activate the "log mirror", it always synchronizes the data from the > master leg to slave leg since it has no log device (as the "log mirror" > uses "corelog"). In other words, the "log mirror" always starts in "not > in sync" state and synchronizes. > > If the master leg is broken for the "log mirror", it starts in "not in > sync" state and tries to copy data from the "broken leg" to the active > leg! This appears as the master leg failure while doing synchronization > which makes the whole device unusable. > >> I'm not sure if I understand his statements about the >> synchronization correctly. Why would any synchronization within the >> data mirror occur at all? It's only the log which is broken, not the >> actual data in vg00-lv00_mimage_0/1. If any synchronization in the >> _data_ mirror occurs just because one leg in the _log_ mirror has a >> problem, I'd consider that a bug. > > Since the entire log device is unusable with its "master device > broken", the "data mirror" goes for synchronization. Thank you for the good explanation, Malahal. You are explaining exactly what I need to say. I'm using LVM2.2.02.43, on which this mirroredlog patch is built. Thanks, Taka -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
