[DRBD-user] Local Asynchronous Replication

Lars Ellenberg lars.ellenberg at linbit.com
Tue Jan 25 11:32:16 CET 2011

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

On Mon, Jan 24, 2011 at 10:34:54AM -0700, Chris Worley wrote:
> On Mon, Jan 24, 2011 at 10:15 AM, Nick Couchman <Nick.Couchman at seakr.com> wrote:
> >
> >> Ah, I see. So you want to retain Read-Only access even when iSCSI is
> >> disconnected? That's problematic, as DRBD will probably detect possible
> >> split-brains and refuse to resume synchronization. You can of course
> >> discard your local backing device upon each reconnect, but that will
> >> trigger (I think) a full sync from the iSCSI device.
> >
> > No, I want full r/w access even when iSCSI is disconnected, then a
> > resynchronization (full resync is fine) when the iSCSI volume is back.
> > I'm not going to be using this in a cluster scenario at all, so DRBD
> > need not worry about split-brain situations, as nothing will be writing
> > to the volume on the iSCSI side besides DRBD.  Essentially, the iSCSI
> > (backup) side will be a read-only copy used for restoring files and DR
> > recovery scenarios.
> I can think of another reason why this might be useful: fabric
> performance.  DRBD is limited to 10GbE performance.

Is that so?
What makes you think so?

> If the primary
> and secondary each served the local drives as targets over SRP (and
> the primary writes as an initiator directly to the secondary's drive),
> for example, the mirror peak write performance could be much higher.

I cannot follow you here.

If that's like some thought through idea, please can you explain?

: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

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