[DRBD-user] Remote failed to finish a request within ko-count * timeout

Lars Ellenberg lars.ellenberg at linbit.com
Tue Oct 28 14:49:29 CET 2014

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, Oct 27, 2014 at 09:25:23AM +0100, D.Gossrau wrote:
> Hello mailing list !
> From time to time I see in /var/log/messages following messages :
> kernel: block drbd1: Remote failed to finish a request within
> ko-count * timeout
> kernel: block drbd1: peer( Secondary -> Unknown ) conn( Connected ->
> Timeout ) pdsk( UpToDate -> DUnknown )
> DRBD version : 8.4.3
> The DRBD manual describes the parameter ko-count as follows:
> ko-count number
>     If a secondary node fails to complete a write request in
> ko-count times the timeout parameter, it is excluded from the
> cluster. The primary node then sets the connection to this secondary
> node to Standalone. The default value of ko-count is 0, which
> disables this feature.
> In my DRBD configuration ko-count is not configured. According to
> the manual I assume the feature is disabled in this case.

It is not unheared of that man pages and actual behavior do not exactly
match, or get out-of-sync over time.

You could have checked what in fact is configured in kernel,
 # drbdsetup 0 show --show-defaults
and it would have told you that your ko-count is 7,
which happens to be the default since 8.4.

> But why are the messages written into the log file ? What's the
> reason for that ? Which parameter needs to be changed to avoid this
> ?

The fact remains that your secondary *was* unresponsive for at least 7 *
timeout seconds, assuming timeout is the default, which is 6 seconds,
that means your secondary did take >= 42 seconds for a single request.

If ko-count had been 0, you most likely would have come here
and complained about a "hung for three minutes" DRBD.

Choose your poison.
Or find and fix the problem in your setup.

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

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