[DRBD-user] Two primaries setup over a Wan Network which broke up frequently...

Julien Reveillet j.reveillet at graphique-alliance.com
Thu Feb 12 17:02:32 CET 2009

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


Hello,

I have a very special configuration to set up.

I need to have 2 servers running CentOs 5 with a mysql server 4.0.21 (
that a must do...).
The data base directory needs to be replicated between both servers with
one mysql server running with read-write access and the other with
read-only access.

The production server (mysqld with rw access) which is highly loaded
needs to not be impacted by drbd accesses ( it can be a little bit ) and
the web server (mysqld with ro access) can be asynchronous for some
minutes with no problems.

For now, i choosed to use drbd 8.2.6 with ocfs2.
It is set up and running correctly on the same lan with a descent sync
rate but i will have to try it soon over a wan network.

On what i've tested and read, i can't use protocol A for this scenario
as the option "allow-two-primaries" needs only protocol C.

The whole database directory is about 70GB which is quite huge to full
sync over a 2M wan network. For sure, i will do the first sync over a
lan but i'm afraid of cases where drbd will go to standalone and will
need a full resync.

So my questions are :

- Falling to standalone mode will automaticly needs a full resync?

- Can this kind of scenario be possible to work on or not ?
(if not, do you think of another solution?)

- Will protocol C cause many heavy lags on my production server ?
(i guess yes but...)

Thanks in advance.

Best Regards.

Julien Reveillet.




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