[DRBD-user] Just restarting secondary causes split brain, can someone expain why please?

David df at auto123.com
Mon Mar 5 23:37:33 CET 2007

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Before reboot:

hydrogen:/etc/ha.d # cat /proc/drbd
version: 8.0.1 (api:86/proto:86)
SVN Revision: 2784 build by root at hydrogen, 2007-03-05 08:47:01
 0: cs:Connected st:Primary/Secondary ds:UpToDate/UpToDate C r---
    ns:264 nr:0 dw:256 dr:580 al:0 bm:2 lo:0 pe:0 ua:0 ap:0
        resync: used:0/31 hits:20 misses:2 starving:0 dirty:0 changed:2
        act_log: used:0/127 hits:25 misses:0 starving:0 dirty:0 changed:0

oxygen:~ # cat /proc/drbd
version: 8.0.1 (api:86/proto:86)
SVN Revision: 2784 build by root at oxygen, 2007-03-05 08:43:02
 0: cs:Connected st:Secondary/Primary ds:UpToDate/UpToDate C r---
    ns:0 nr:264 dw:264 dr:0 al:0 bm:2 lo:0 pe:0 ua:0 ap:0
        resync: used:0/31 hits:20 misses:2 starving:0 dirty:0 changed:2
        act_log: used:0/127 hits:0 misses:0 starving:0 dirty:0 changed:0


During hydrogen reboot:
oxygen:~ # cat /proc/drbd
version: 8.0.1 (api:86/proto:86)
SVN Revision: 2784 build by root at oxygen, 2007-03-05 08:43:02
 0: cs:WFConnection st:Primary/Unknown ds:UpToDate/DUnknown C r---
    ns:0 nr:264 dw:520 dr:316 al:0 bm:2 lo:0 pe:0 ua:0 ap:0
        resync: used:0/31 hits:20 misses:2 starving:0 dirty:0 changed:2
        act_log: used:0/127 hits:25 misses:0 starving:0 dirty:0 changed:0


Started drbd (no heartbeat) on hydrogen
oxygen:~ # cat /proc/drbd
version: 8.0.1 (api:86/proto:86)
SVN Revision: 2784 build by root at oxygen, 2007-03-05 08:43:02
 0: cs:StandAlone st:Primary/Unknown ds:UpToDate/DUnknown   r---
    ns:0 nr:264 dw:520 dr:316 al:0 bm:2 lo:0 pe:0 ua:0 ap:0
        resync: used:0/31 hits:20 misses:2 starving:0 dirty:0 changed:2
        act_log: used:0/127 hits:25 misses:0 starving:0 dirty:0 changed:0

On hydrogen, I'm seeing:
hydrogen:~ # service drbd start
Starting DRBD resources:    [ d0 s0 n0 ].
..........
***************************************************************
 DRBD's startup script waits for the peer node(s) to appear.
 - In case this node was already a degraded cluster before the
   reboot the timeout is 0 seconds. [degr-wfc-timeout]
 - If the peer was available before the reboot the timeout will
   expire after 0 seconds. [wfc-timeout]
   (These values are for resource 'r0'; 0 sec -> wait forever)
 To abort waiting enter 'yes' [ 520]:



So just starting drbd on hydrogen causes a split brain and oxygen, now 
the primary, to go into a standalone state.  Why is that?  The file 
system is mounted as a read only file system so no changes should be 
taking place. This is not a primary/primary setup so there is only one 
"active" node at a time. I was under the impression that the rebooting 
node, hydrogen, should see that it is out of date and become secondary, 
resync itself with the primary and stay in the secondary state until 
that is changed?  Am I wrong?

Both systems are identical:
SLES 10
kernel 2.6.16.27-0.9-bigsmp
drbd 8.0.1 compiled from source


Thanks ahead,

David





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