Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
/ 2006-10-02 16:25:04 -0700 \ Robinson, Eric: > Lars said... > > <snip> > --------------------------------------- > I'll quote the code, to clarify the intention for when > "degr-wfc-timeout" is used: > /* If I am currently not Primary, > * but meta data primary indicator is set, > * I just now recover from a hard crash, > * and have been Primary before that crash. > * > * Now, if I had no connection before that crash > * (have been degraded Primary), chances are that > * I won't find my peer now either. > * > * In that case, and _only_ in that case, > * we use the degr-wfc-timeout instead of the default, > * so we can automatically recover from a crash of a > * degraded but active "cluster" after a certain timeout. > */ > --------------------------------------- > </snip> > > Hmmm... why not always start both nodes as Secondary with no timeout, > then let heartbeat force the right one to be Primary? Wouldn't that > avoid blocking and split-brain? thats why it is configurable... just make sure that your heartbeat won't decide to make a node primary that happens to have long-since outdated data cluster fine secondary crash [first spike of a brown out] time passes primary crash [well, now its a real black out] ... [power back] previously secondary comes up, heartbeat decides to make it primary *** you are primary with outdated data *** previously primary needs a lot longer (recounts its scsi devices, thinks it needs to fsck its root, whatever)... same effect as split brain: diverging data sets. > Is it possible to set up something like this... > > Cluster fine, connected. > Pull plug from primary machine A. > Heartbeat on B takes over, forces drbd on B to be primary. > Plug machine A back in. > Heartbeat on A detects it is secondary, forces drbd on A to go > secondary. > > If this is a stupid question, forgive me. I am shameless about showing > my ignorance. :-) well, it depends what plug you pull, and what you can teach heartbeat to detect. -- : Lars Ellenberg Tel +43-1-8178292-0 : : LINBIT Information Technologies GmbH Fax +43-1-8178292-82 : : Schoenbrunner Str. 244, A-1120 Vienna/Europe http://www.linbit.com : __ please use the "List-Reply" function of your email client.