[DRBD-user] dual primary mode with which FS

Digimer linux at alteeve.com
Tue Mar 23 20:07:48 CET 2010

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

On 10-03-23 02:50 PM, Florian Haas wrote:
> On 03/23/2010 07:35 PM, Michael Schwartzkopff wrote:
>> Am Dienstag, 23. März 2010 17:08:56 schrieb Digimer:
>>> On 10-03-23 10:02 AM, Florian Haas wrote:
>>>> On 2010-03-23 14:52, Michael Schwartzkopff wrote:
>>>>> Am Freitag, 19. März 2010 14:12:30 schrieb Andreas.Ruetten at hansenet.com:
>>>>>> Hi list,
>>>>>> first of all please answer also to my email-address because I'm not
>>>>>> subscribed to the ML.
>>>>>> Here are my questions:
>>>>>> I have to set up drbd 8.0.14 (Debian stable) in dual-primary mode.
>>>>>> One node has to read and write while the other node only need read
>>>>>> access.
>>>>>> Do I need GFS or OCFS?
>>>>> Not really if you can be sure that the second node ONLY reads.
>>>> Are you nuts? I thought you wrote books about this!
>>>>>> Or would a simple etx3 sufficient enough?
>>>>> Yes. Mount option "read-only" in the second node.
>>>> I repeat my above statement.
>>>> I'm totally baffled right now.
>>>> Andreas: you want to put a filesystem on dual-Primary DRBD, it has to be
>>>> a cluster filesystem. No ifs, buts, or maybes.
>>>> Question is, do you really need dual-Primary DRBD? You most probably
>>>> don't.
>>>> Florian
>>>    From a purely technical view point, Michael isn't wrong. If the second
>>> node never changes a single block on the DRBD partition, it can't
>>> technically hurt it. Of course, you'd need to make sure that the node's
>>> DRBD doesn't try to recover from failures without first fencing the
>>> other node.
>>> It's not wise, but it's not impossible, either.
>> didn't have my best day today. Although it should be possbile I did not say it
>> is wise to do.
> To wrap this up: don't do this. Ever. The reasons have been mentioned in
> this thread. Data divergence, and violation of cache coherency.
> Florian

Agreed, bad idea.

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