[DRBD-user] Kernel hung on DRBD / MD RAID

Andreas Bauer ab at voltage.de
Tue Feb 21 15:26:57 CET 2012

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

From:	Felix Frank <ff at mpexnet.de>
Sent:	Tue 21-02-2012 10:05

> On 02/21/2012 12:03 AM, Andreas Bauer wrote:
> > So when vm-master is Primary, vm-slave is Secondary, and I force-detach the 
> backing device on vm-master, DRBD will automatically make vm-slave the Primary 
> and direct writes to that host?
> no.
> The secondary remains secondary. However, the primary cannot write to
> its local disk (seeing as it is detached), so writes are done *only* on
> the secondary (normally, any write is done on both nodes).
> When the diskless node eventually gets access to a backing storage
> device again (the old disk or a new one), it resyncs with the UpToDate
> one and you're back to normal.
> Of course, if you loose connectivity or the peer's disk, you're down to
> "no disk", and therefore out of operation.
> HTH,
> Felix

Thanks, it does help. So a node can be Primary and inconsistent while the opposite node is Secondary and UpToDate and read requests are (necessarily) satisfied over network. Didn't know that.



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