[DRBD-user] disconnecting hangs after ko-count failure

Lars Ellenberg lars.ellenberg at linbit.com
Tue Jan 22 19:16:55 CET 2008

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


On Tue, Jan 22, 2008 at 06:01:12PM +0100, Walter Haidinger wrote:
> > >     timeout       100;    # < (connect-int|ping-int), (unit = 0.1
> > seconds)
> > >     connect-int   30;    # (unit = 1 second)
> > >     ping-int      60;    # (unit = 1 second)
> > >     ping-timeout  50;    # (unit = 0.1 seconds)
> > 
> > interessting timout settings, but drbd over openvpn over 11MBit WLAN
> > is strange enough in itself, so if it works for you...
> 
> I just wanted to make sure that there are no timeouts for drbd due to network latency. The values are rather conservative, obviously.
> 
> > 
> > >     max-buffers         256;
> > 
> > I seriously recommend a much higher setting here.  do at least 2000.
> > high latency "flaky" network with low max-buffers setting...
> > may even be the root cause of the symptoms you are seeing.
> 
> The man page says to increase max-buffers for high performance. 11
> Mbit WLAN is rather low-performance so I figured that a small
> max-buffers value won't hurt. I'd call the man page a bit misleading
> here! ;-)

no, well, the manpage is "basically" correct.

and it should just work fine with low max-buffers.  even though testing
with very low max-buffer settings went fine - certainly every topology
is different. and we have had a resource starvation deadlock in some
obscure cases with too low max-buffers; there may be an other one
lurking...

and, well, max-buffers should be increased when you expect to have more
buffers in flight. which usually means you have a high performance io
subsystem; but may also mean you just have high latency :->
so, yes, we probably should say "increase to the amount of expected in-flight io".

-- 
: Lars Ellenberg                           http://www.linbit.com :
: DRBD/HA support and consulting             sales at linbit.com :
: LINBIT Information Technologies GmbH      Tel +43-1-8178292-0  :
: Vivenotgasse 48, A-1120 Vienna/Europe     Fax +43-1-8178292-82 :
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