[DRBD-user] Clarification on How-To

[Alan Robertson]

Nuno Tavares wrote:
>> From: Alan Robertson <alanr at unix.sh>
>> To: John Lange <john.lange at bighostbox.com>
>> CC: drbd <drbd-user at linbit.com>
>> Subject: Re: [DRBD-user] Clarification on How-To
> 
> 
>>> Since the config files is not designed to indicate a primary node, how
>>> does drbd know which node shoul
> 
> 
> Each DRBD device keeps an internal state which will allow to determine 
> which one is the most up-to-date (should read last-changed) node, 
> between the two hosts connecting. This way the DRBD will always know 
> which is the *best* DRBD to mirror from.
> 
> You can surpass this behaviour by using a cluster manager (like 
> Heartbeat), or doing it manually using drbdadm/drbdsetup.

DRBD will never knowingly use out of date, and heartbeat will not override 
that.  Only humans can override that IIRC.  On older implementations it 
will refuse to fail over to the side with old data.  On recent versions, it 
will allow updates from either side, but it still uses the best copy of the 
data (until they are updated to be the same).




-- 
     Alan Robertson <alanr at unix.sh>

"Openness is the foundation and preservative of friendship...  Let me claim 
from you at all times your undisguised opinions." - William Wilberforce