[Drbd-dev] [PATCH] drbd: create new uuid even we dont have quorum

[Xu Rui]

Hi Joel,
Thanks for the reply. I have a 3 node cluster and all 3 nodes running with DRBD9.0: Primary node is
node-1,  and Secondary nodes are node-2 and node-3, quorum is configured as 2.


After some more investigation, I found the root cause of this problem we met is that NEW_CUR_UUID
will clear whether a new uuid was actually generated in make_new_current_uuid.


You can reproduce this problem on DRBD9.0 through the following steps:
(1) network failure on node-2
(2) network failure on node-3
(3) write on node-1(will suspend since quorum loss)
(4) node-2 network recovery
(5) node-3 network recovery
you will find that data on node-3 is inconsistent with two other nodes.


I also find this problem is not exist in DRBD9.1  since the code of inc_ap_bio_cond
in DRBD9.1 is different from that in DRBD9.0, so i have sent a patch for this bug in
DRBD9.0:


https://lists.linbit.com/pipermail/drbd-dev/2022-April/006576.html

So you can go to review my new patch directly.
By the way, have you focused on DRBD9.1 and is there a stable verison of it?
Thanks,
Xu

From: Joel Colledge <joel.colledge at linbit.com>
Date: 2022-04-07 18:48:12
To:  Rui Xu <rui.xu at easystack.cn>
Cc:  Philipp Reisner <philipp.reisner at linbit.com>,drbd-dev at lists.linbit.com,dongsheng.yang at easystack.cn
Subject: Re: [PATCH] drbd: create new uuid even we dont have quorum>Hi,
>
>When quorum is configured, we expect not to have split-brain
>situations. Hence it is important that we do not generate new UUIDs
>until they are definitely necessary. When we do not have quorum, no
>writes should complete, so we do not need to generate a new UUID. We
>may need to generate one before we regain quorum instead.
>
>That said, there have been various bugs in the implementation. Try to
>reproduce your issue with the latest drbd-9.1. If it can still be
>reproduced, then describe the exact reproduction steps and we can
>discuss the appropriate fix.
>
>Best regards,
>Joel




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