[DRBD-user] Why not keep track of peer outdated on up node?

Lars Ellenberg lars.ellenberg at linbit.com
Tue Mar 10 09:39:05 CET 2009

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, Mar 09, 2009 at 10:59:46AM -0700, Martin Fick wrote:
> However, if you keep track of your peer's failure,
> this restriction is potentially removed.

We keep track of the peer being "outdated",
if it is.

We do not keep track of "peer's failure",
because we don't know about that.

> If node
> B suffers an HD failure and you are replacing its
> drive, do you want your cluster to require manual
> boot intervention if node A happens to go down
> for a minute?

if it "goes down" _unexpectedly_,
it will be a crashed primary,
and use the "degr-wfc-timeout".
which is finite by default.
no manual intervention needed.

if it is _shut down_ cleanly, explicitly,
then well, you had manual intervention anyways.

that is currently the reasoning behind how we deal
with wfc-timeout, and degr-wfc-timeout.

> Seems unnecessary to me, node A
> should be smart enough to be able to reboot and
> continue on its own?

but yes, we do consider to not wait at all _iff_ we find the "peer is
outdated or worse" flag in the meta data. the flag is already there.

> Well, it certainly can be handled on the cluster level
> (and I plan on doing so), but why would drbd not want
> to store extra important information if possible?

it already does.

it just does not (yet) use it to skip the wait-for-connection
completely. this can probably be changed.
this has some more implications though, which we are discussing.

> Even if drbd does not use this info, why not store the
> fact that you are positive that your peer is outdated

we already do.

> (or that you are in split brain)?!

hm.  we probably could.  but what would we then do with that
information?  just display it?

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

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