[DRBD-user] Local Asynchronous Replication

Chris Worley worleys at gmail.com
Mon Jan 24 18:34:54 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 10:15 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.  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.

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