Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
/ 2006-09-19 16:44:14 +0200
\ Maciej Bogucki:
> Hello,
>
> I've been using drbd for the past few years without any problems, but now my problem is a strange one.
> I have HA mysql server with drbd 0.7.21 and kernel 2.6.17. When mysql
> Partition (mysql databases) is on drbd device(datadb), server gets
> lags - no response for 1-4seconds. It isn't network related problem(there in no packet lost!!), but
> console (keyboard and monitor are directly connected) and all processes on server hangs too! The problem only
> apears when mysql database is on drbd device, and everything is working fine when I move data to non drbd
> device(sda). So I'm sure that it is drbd or kernel problem. When I migrate mysql to secondary machine, I have the
> same problems, so I think that hardware is ok :)
> The same problem is with drbd 0.7.17 with kernel version 2.6.14.
> The strangest thing is, that I have the same hardware and
> Software (drbd,kernel) in another location and there is no problems. One
> change is that there I have apache instead of mysql.
> Any ideas?
outside drbd:
verify what io scheduler you use.
I'd recommend to use "deadline" on servers.
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 ...
well, if there would be a "one-fits-all" setting,
these won't be configuration parameters, right?
> Here is my drbd.conf
>
> resource datafs {
> protocol C;
> incon-degr-cmd "echo '!DRBD! pri on incon-degr' | wall ; sleep 60 ; halt -f";
I know the "halt -f" is in the example config, but you may want to
consider to write something like "sleep <verylargenumber>" or
"killall -9 heartbeat ccm ipfail" instead...
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