[DRBD-user] How to use drbd to upgrade highly available application?

Knight, Doug dknight at wsi.com
Fri Sep 5 20:08:15 CEST 2008

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


I am working on a strategy to upgrade my real time highly available
application that uses a drbd resource as its file system for its
database. I am using drbd 8.2.5 and heartbeat 2.1.3, on a CentOS 5.2
server pair. The idea goes something like this:


1.	Set drbd on the Primary host to StandAlone, so that the real
time app continues to run, but releasing the drbd resource on the
Secondary host
2.	Mount the drbd resource on the secondary, delete the database
3.	Upgrade the real time app and its database on the Secondary host
4.	Switch the running real time app to the Secondary host
5.	Reconnect the drbd resource on the Primary host to the Secondary
host, and resync from Secondary to Primary


I've gone over the drbdadm tool, and I think the steps are something


(on Primary) drbdadm disconnect pgsql

(on Secondary) drbdadm primary pgsql; mount /dev/drbd0 /mirror

Upgrade app and db on Secondary

Switch running app to Secondary

(on Secondary) drbdadm invalidate-remote pgsql

(on Primary) drbdadm connect pgsql


Can someone confirm that I've got the right commands and in the right
order? Have I provided enough info? Its one of those things where I know
I could probably hose the servers if I don't do it right, and I've
pretty much got one shot to get it right.


Thanks for your help,

Doug Knight

WSI Corp


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