On 16/07/2013 14:55, Brian Candler wrote:
* Check /proc/drbd on target, require network is Connected and local
disk is UpToDate. [No check on source?]
* on target: drbdsetup <dev> secondary (just to be sure?). No wait or
status check?
* on both nodes: drbdsetup <dev> disconnect. No wait or status check?
Actually it does wait for GetProcStatus().is_standalone (i.e. connection
status StandAlone)
* on both nodes: drbdsetup <dev> connect. Poll /proc/drbd until
connected or syncing
More precisely, the code is doing the following on both sides (roughly
simultaneously) to reconnect in multi-master mode:
drbdsetup <dev> syncer -r 61440 --create-device
drbdsetup <dev> net ipv4:x:x ipv4:y:y C -A discard-zero-changes -B
consensus --create-device -m -a md5 -x XXXXXX
You said:
" Apparently a node was promoted right in the middle of a resync
handshake, and did not like that at all."
Now, I'm not clear which bit is the "promotion": It looks like
"drbdsetup <dev> connect ... -m" both reconnects *and* promotes to
master in one step.
Now if there has been a write to the primary disk during the short time
period when the secondary is disconnected from the primary, and then we
reconnect in dual-master mode, then it's expected to do some resync
along with the promotion. This appears to work: if I configure the VM to
write aggressively to disk, then migrate, I see it goes through a resync
phase:
0: cs:Connected ro:Secondary/Primary ds:UpToDate/UpToDate C r-----
0: cs:StandAlone ro:Secondary/Unknown ds:UpToDate/DUnknown r-----
0: cs:WFConnection ro:Secondary/Unknown ds:UpToDate/DUnknown C r-----
0: cs:SyncTarget ro:Primary/Primary ds:Inconsistent/UpToDate C r-----
0: cs:Connected ro:Primary/Primary ds:UpToDate/UpToDate C r-----
0: cs:StandAlone ro:Primary/Unknown ds:UpToDate/DUnknown r-----
0: cs:WFBitMapS ro:Primary/Secondary ds:UpToDate/Consistent C r-----
0: cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate C r-----
So the race seems to be elsewhere.
To answer your other question: no I've not tried building any other
version of drbd, I'm just using the stock one in Debian Wheezy.
Regards,
Brian.
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