[DRBD-user] data-integrity-alg in dual-Primary setup

Lars Ellenberg lars.ellenberg at linbit.com
Fri Sep 17 14:40:20 CEST 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 Fri, Sep 17, 2010 at 11:22:53AM +0200, Fabrice Charlier wrote:
> Hi,
> Three months ago we deployed a "web cluster" for LAMP hosting. We
> based this solution on drdb in active/active mode combined with
> ocfs2. This solution matches correctly our needs but several times (
> ~ once a month) a problem appears: we have enable the
> "data-integrity-alg" option to (try to) avoid silent corruption of
> data and several times, this feature detected that data have been
> altered during transit between the two nodes. As we have
> active/active nodes and as we use automatic split brain recovery
> policies proposed in official documentation, the two members of the
> mirror are disconnected and we have to resync it manually to
> continue normal operation. We have already disabled all TCP
> offloading capabilities of all NICs without success.
> Is it possible to ask drdb to retry to send the block until success
> in this kind of situation?

It is likely one of those cases where in-flight buffers are changed.
Problem is known since a long time, but recently has drawn some
more attention again,

Maybe disable the drbd level checksum, and trust the TCP checksum.

> If not, are you planning to implement this feature?

But it does not have particular priority.
Maybe we rather wait for the VM and VFS layer to fix it for us.

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

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