> > I would suggest that you simply get raid1 to block any write requests > > until all drive failures have been acknowledged by userspace. > > So you would need to differentiate between an acknowledged drive > > failure and an unacknowledged failure. Writes block when ever there > > are unacknowledged failures. > > Then you need a message that can be sent to the raid1 to acknowledge > > the failure of a particular device. > > 'suspend' would need to fail if there are any unacknowledged failures > > as otherwise it would block. > > As we discuss in this thread, your suggestion is quite similar to what > malahal proposed more than one year ago. > > 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 is a simple approach, but all write I/Os are blocked before write > errors are processed by userspace (dmeventd). Depending on the error, > such as timeout, the recovery procedure in userspace may take a long > time and application sensitive to delay will have another problem. > > superblock approach may solve this data corruption issue without an > additional delay. When dm-raid1 detects a write error, it can disable > the mirror leg quickly and ask userspace to process aftertreatment. > > I would like to continue discussion how to fix this issue. > > Thanks, > Taka The current code already blocks all i/os if the log fails. So if your application is sensitive for it, you have to test for it anyway. You can write new implementation dm-raid1.2 that will have two log devices (just like md-raid has two superblocks) and can perform without userspace intervention if any of the legs or logs fail. But it is really more like rewrite --- I think it would be easier to write it from scratch than to patch it over existing dm-raid1 code. Mikulas -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
