malahal@xxxxxxxxxx wrote: > Takahiro Yasui [tyasui@xxxxxxxxxx] wrote: >> malahal@xxxxxxxxxx wrote: >>> Look at this patch >>> http://permalink.gmane.org/gmane.linux.kernel.device-mapper.devel/4973 >>> >>> It essentially generates an uevet and waits for the user level code to >>> act on it and send a message to unblock it. >> This patch was posted more then a year ago, and I could not find >> any discussion on this issue/patch in the mailing list archive. >> What was the conclusion of the discussion about this patch? >> Are there any discussions outside this mailing list? > > The patch alone can't fix the issue. It needed LVM changes. We had some > discussions on how to implement the LVM related changes. Finally I was > told look at remote-replication target code to see how that handles > selecting the right "MASTER" device. That code is not published yet. Who is working on this? > That is how the "log device" failure is handled today. Alasdair also > thought we needed to change LVM to handle events as soon as possible > using a single thread and not block behind an LVM scan, etc. I agree. I also described this point in the background section of "Introduce metadata cache". https://www.redhat.com/archives/lvm-devel/2009-April/msg00014.html > Another method is to have dm-mirror target metadata on the disk itself. > This metadata is internal to the kernel module and would NOT touch it. > This would avoid any user level interaction and delays. I'm interested in this approach that dm-mirror manages own data to keep the status, such as the number of default mirror, valid legs. When an error is detected, dm-mirror handles the error and disable the error disk as soon as possible in kernel space, then lvm metadata is managed in the user-space later. Some transaction systems are sensitive to delay, and approaches which don't cause much delay even if an error was detected are desirable. > Of course, we can do something in the log itself but it will not fix > "corelog" mirrors, more over the system can't auto recover after a > missing log alone. Yes, storing information on the log device does not save "corelog" mirrors, so we might need some area to keep information on mirror legs. Thanks, Taka -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
