On Wed, Oct 17, 2018 at 03:11:42PM -0400, Digimer wrote: > On 2018-10-17 5:35 a.m., Adam Weremczuk wrote: > > Hi all, > > > > Yesterday I rebooted both nodes a couple of times (replacing BBU RAID > > batteries) and ended up with: > > > > drbd0: Split-Brain detected but unresolved, dropping connection! > > Fencing prevents this. > > > on both. > > > > node1: /drbd-overview// > > //0:r0/0 StandAlone Primary/Unknown UpToDate/DUnknown /srv/test1 ext4 > > 3.6T 75G 3.4T 3% / > > > > node2: /drbd-overview // > > //0:r0/0 StandAlone Secondary/Unknown UpToDate/DUnknown/ > > > > I understand there is a good chance (but not absolute guarantee) that > > node1 holds consistent and up to date data. > > > > Q1: > > > > Is it reasonably possible to mount /dev/drbd0 (/dev/sdb1) on node2 in > > read only mode? > > > > I would like to examine the data before discarding and syncing > > everything from node1. > > Yes. You can also promote node 2 to examine it as well. > > > /drbdadm disconnect all// > > //drbdadm -- --discard-my-data connect all/ > > Discarding the data will trigger a resync and resolve the split-brain, > but of course, any changes on the discarded node will be lost. > > > Q2: > > > > Will the above completely purge all data on node2 or just drbd metadata? > > > > I.e. will all 75G have to be fully copied block by block or a lot less? > > It will do a full resync.
Even after a "split brain" (rather: data divergence), DRBD usually can do an "incremental, bitmap based" resync: DRBD knows which blocks have changed on each node, and will sync the blocks described by the bit-or of those out-of-sync bitmaps. > > I'm concerned about time and impact on performance when it comes to > > terabytes of data. > > > > Regards, > > Adam > > The resync (on 8.4) adapts the resync rate to minimize impact on > applications using the storage. As it slows itself down to "stay out of > the way", the resync time increases of course. You won't have redundancy > until the resync completes. > > -- > Digimer > Papers and Projects: https://alteeve.com/w/ > "I am, somehow, less interested in the weight and convolutions of > Einstein’s brain than in the near certainty that people of equal talent > have lived and died in cotton fields and sweatshops." - Stephen Jay Gould -- : Lars Ellenberg : LINBIT | Keeping the Digital World Running : DRBD -- Heartbeat -- Corosync -- Pacemaker DRBD® and LINBIT® are registered trademarks of LINBIT __ please don't Cc me, but send to list -- I'm subscribed _______________________________________________ drbd-user mailing list [email protected] http://lists.linbit.com/mailman/listinfo/drbd-user
