[DRBD-user] Re: drbd 0.7.21(kernel 2.6.17) hang problem

Lars Ellenberg Lars.Ellenberg at linbit.com
Thu Sep 21 11:53:11 CEST 2006

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


/ 2006-09-21 11:12:59 +0200
\ Maciej Bogucki:
> >>>in drbd:
> >>>you could play with "unplug-watermark" and "max-epoch-size" (and
> >>>possibly max-buffers).
> >>>when I say "play", I mean it.  it could get better if you increase,
> >>>it could get better when you decrease, it could get better if you
> >>>adjust in opposite directions (where possible), and it could happen to
> >>>have no noticable effect at all, which is all very dependent on your
> >>>lower level io subsystem and on network timings and ...
> >>
> >>I know, than I can play with them, but there is another strange
> >>thing. When I disconnect secondary node(shutdown heartbeat, and
> >>drbd) I get lags also. Also I don't have much traffic on
> >>database(1256 writes per minute - so I's 20KB per seconds, and only
> >>a few reads per minute), so playing with "net" parameters is not
> >>necessary in my case.  I think that it is drbd bug or some stupid
> >>thing :)
> >what about al-extends?
> I have play with it(increase and decrease one) without positive results :(
> 
> >how often do the bm: and al: numbers increase in /proc/drbd?
> >(watch -n1 cat /proc/drbd, and look at that)
> They don't change often, only a few single(+1) increases per hour.

well, then leave al-extents on its default value, because then it is not
expected to have any effect!

> al-extends, and all "net", "syncer" directives have only sense when there is another node.

no.  I asked specifically about al-extends and the frequence the bm: and al:
counters increase because that is the only overhead drbd has when in
disconnected mode. if they only move infrequently, then you don't have
drbd overhead here.

> When I only leave one node(primary) I still have laga. And it is
> strangest thing to me.  It is x86_64 HA Cluster, but I have the same
> hardware in another location and there are no problems. Strange :)

right. so I'll file that as "somebody elses problem",
as it seems not to be drbd problem.

-- 
: Lars Ellenberg                                  Tel +43-1-8178292-0  :
: LINBIT Information Technologies GmbH            Fax +43-1-8178292-82 :
: Schoenbrunner Str. 244, A-1120 Vienna/Europe   http://www.linbit.com :
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