AW: [DRBD-user] Primary SyncTarget and dead Secondary SyncSource duringsynchronization.

Martin Bene martin.bene at
Thu Jul 14 07:19:10 CEST 2005

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

Hi Igor,
> Few weeks ago there was discussion about how Primary can be 
> SyncTarget.
> As I understand, the only way is to begin synchronization as 
> a SyncSource, than switch to Primary state.

You get that stae only when
 1) connecting drbd with both sides secondary
 2) resync needed (sync will start right after connect)
 3) make drbd primary on the sync target.

I think the most probable cause to get 1+2 to happen is that both nodes
go down at the same time due to power failure. When using heartbeat, 3
will only happen if the services were not running on their "home node"
at the time of power failure.

> But what will happen with Primary SyncTarget when Secondary SyncSource
> will die before the end of synchronization?

A primary sync target that loses the connection to the sync source no
longer has access to good data. The only thing it can do at that point
is panic (which it does). Since both reads and writes go to the sync
source on a primary sync target, the sync source still has a consitent
copy. You must get the sync source back online to access your data

To actually hit this in a production system you need a whole series of
 - heartbeat services moved off their default nodes (after failures or
by admin)
 - crash of both nodes at the same time
 - another crash of the sync source after rebooting both nodes.

Bye, Martin

More information about the drbd-user mailing list