[DRBD-user] DRBD Truck Based Replication Inconsistently Working

Justin Patriquin jpatriquin at pantelintl.com
Mon Aug 15 18:00:23 CEST 2016

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


I'm currently trying to get a system up and running using DRBD. A lot of 
data has already accumulated on the system so I needed to use a truck 
based replication solution. I migrated all of the data on to a DRBD 
partition on NODE 1 and then used the following commands to copy the 
data onto a portable hard drive that would be used to ship the data to 

drbdadm disconnect ha

drbdadm new-current-uuid --clear-bitmap ha

dd if=/dev/sda1 of=/dev/sdb1 bs=4096 conv=noerror,sync (/dev/sda1 = the 
device of drbd partition, /dev/sdb1 = the portable hard drive partition 

drbdadm new-current-uuid ha

drbdadm connect ha

On NODE2 the following commands would then be run once the portable hard 
drive arrives there:

dd if=/dev/sdb1 of=/dev/sda1 bs=4096 conv=noerror,sync (/dev/sda1 = the 
device of drbd partition, /dev/sdb1 = the portable hard drive partition 

drbdadm connect ha

The issue occurs here where it begins syncing all of the data from NODE 
1 to NODE 2. It should only be syncing the data since the first 
new-current-uuid. This happens inconsistently. Sometimes it will work as 
expected and sometimes it won't. Doing some diagnostics I was able to 
determine that the UUIDs that were copied onto the portable hard drive 
were UUIDs from before the first new-current-uuid. It appears the UUIDs 
didn't get properly flushed to disk before the dd command was run. I 
think I was able to get it to work consistently on my test system by 
bringing the resource down and back up again after the first 
new-current-uuid command and before the dd. I need to implement this on 
a production system and want more confidence that this will work so 
figuring out the root cause would be ideal. Any advice or help would be 
much appreciated.

The hard drives on both NODE 1 and NODE 2 are currently running under 

DRBD Version: 8.4.7-1


Justin Patriquin | Software Developer
Pantel International |
125 Joseph Zatzman Drive | Dartmouth, Nova Scotia | B3B 1W1
Phone: (902) 468-5998

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