[DRBD-user] Ahead / Behind Log Messages

Lars Ellenberg lars.ellenberg at linbit.com
Tue Nov 12 12:43:16 CET 2013

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, Nov 11, 2013 at 11:34:26AM -0600, J.R. Lillard wrote:
> I'm using Ahead / Behind mode on all my stacked resources.  I just noticed
> this morning that when a resource falls behind it spews tens of thousands
> of messages into my syslog.  Can this be turned off?  Over the last 6 hours
> I've received about 60,000 messages like this one.
> kernel: [1012720.805407] block drbd50: w_start_resync later...
> And 10,000 of these.
> kernel: [1003951.022263] block drbd10: Congestion-fill threshold reached
> 2,500 of these.
> kernel: [1011032.612898] block drbd50: Congestion-extents threshold reached

The ahead/behind mode is meant to be used with drbd-proxy,
which has a much higher "buffer size".
So you typically get a nice hysteresis
 reach threshold,
 take some minutes to drain,
 go back into resync,
 go back into live replication
 possibly repeat on next "congestion" event (write burst).

If you try with too low thresholds,
it may flip-flop between those states very quickly.

No, we don't intend to suppress state change log messages.

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

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