Re: [PATCH 00/16] DRBD: a block device for HA clusters

[Philipp Reisner]

[...]
>
> Well, you have to agree that during a resync from the activity log,
> which plays up the primary disk from one end to another, the secondary
> is completely corrupt if a primary failure occurs before the resync
> completes.  That's something that's triggered by a network outage, and
> so is a far more common event than cascading dual failures.  It's all
> really a question of where you focus your effort to eliminate the corner
> cases.
>

I fully agree. Just not not leave this unanswered: With DRBD we provide
a snapshot-resync-target handler. By using LVM's snapshotting
mechanism a snapshot is taken before it becomes resync-target. In
case the resync completes gracefully, the snapshot is automatically
removed.

Which is still inferior to a full transaction log on the secondary.

-Phil

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