Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Thu, Sep 08, 2011 at 04:52:28PM +0200, Florian Haas wrote: > On 09/08/11 15:06, SlingPirate wrote: > > > > I have 3 servers two are to run in dual primary mode (node 1 and 2) while a > > third (node 3) is to be an off-site backup. I have got the first 2 nodes > > sync'd and in primary mode quite happily but I can't get the backup node to > > sync. Every time I try to bring the stacked resource into primary on node 1 > > (even with node 2 in secondary) it complains that it "needs access to > > UpToDate data". > > > > Am I just doing things wrong by trying to do a dual primary with a stacked > > backup? > > Yes. This can't work. Well. You can do this: [ upper Primary node 1 ] ---- [ upper Primary node 2 ] [ lower DRBD node 1 ] `------.[ DR node ] And live with the fact that, if you lose node 1, you lose your DR link. If you want to resume the DR replication from node 2, you need a full sync to the DR site. [If you do a planed migration of the DR link to node 2 (no crash involved), you can do so without a full sync to the DR site, but you'd need to know more DRBD internals than are good for me :-)] If you lose node 1 catastrophically, and you now need to resume the DR replication from node 2, you will still need a full sync to the DR site. This can not work: [ upper Primary node 1 ]------------------------------------------ [DR ] [ lower Primary node 1 ]-----[ lower Primary node 2 ] Because there is no way for writes from node2 to reach DR in this picture, [DR] would receive only half of the writes, thus have a corrupted dataset by design. Maybe you don't need dual primary anyways? Very few installations actually do. -- : Lars Ellenberg : LINBIT | Your Way to High Availability : DRBD/HA support and consulting http://www.linbit.com DRBD® and LINBIT® are registered trademarks of LINBIT, Austria. __ please don't Cc me, but send to list -- I'm subscribed