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Two node noSAN : Power failure 8 years 3 weeks ago #703

Hello,

We have a two node noSAN install of HA-Lizard. Today, we have try to unplug the power of the two node. Then we have start the two node.

What is the default behaviour for this situation with DRBD ? We have see that the two node sync but we have lost some data. DRBD will merge the data between the two storage ?

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Two node noSAN : Power failure 8 years 3 weeks ago #705

  • Salvatore Costantino
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Once the DRBD resource reconnects, the primary DRBD device will sync its contents to the secondary. Since we run in Primary/Secondary DRBD mode the sync will always be in one direction
Primary -> Secondary device

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Two node noSAN : Power failure 8 years 3 weeks ago #708

Can we imagine something like this :

VM is running on the Node1
Node1 shutdown because a power outage
Node2 will be the master. I create new data (create a large file) in a VM in Node2
Node2 shutdown because a power outage

If I start first Node2 and then Node1, for me, the new data will be keep and sync to the secondary device (Node1). I keep my data.

If I start first Node1 first and then Node2, the new data will keep ?

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Two node noSAN : Power failure 8 years 3 weeks ago #709

  • Salvatore Costantino
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No HA solution can account for all possible types of HW failures. Although the situation in your example could be very rare, it is possible. In this case, the administrator should be careful to turn on whichever server was the Master last to avoid the slave from becoming a master itself.

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