[DRBD-user] How long will the primary DRBD continue to run without a secondary?

Roland Kammerer roland.kammerer at linbit.com
Mon Jun 18 08:56:28 CEST 2018

On Thu, Jun 14, 2018 at 07:07:35PM -0500, G C wrote:
> I know the secondary is the DR and the primary keeps track of what is
> changing but how long can it continue to run in this state before it will
> cause it to crash or not be writable any longer?  I would gather that at
> some point it would cause a lack of resources to write the changes to but

No, you have a wrong understanding of how DRBD works. It does not store
a log of all changes and then runs out of space. It stores a bitmap in
memory (and important information on disk in *preallocated* meta data).
All in all tiny bits of information are saved *which parts* of the disk
changed, but not *what the content was*.  You can run a disconnected
Primary for ever. So you have a series of "oh part X changed, let me set
the corresponding bits for it, oh part X changed again, let me set the
same corresponding bits again,..."

> I'm not sure and can't find any information related to it.

See the user guide at https://docs.linbit.com

Regards, rck

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