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

Florian Haas florian.haas at linbit.com
Fri Sep 5 21:54:32 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.

Knight, Doug wrote:
> All,
> 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

This description is likely to confuse everyone including yourself,
because you are referring to a host that most of the time will be in
Primary mode as "Secondary" and vice versa.

And before I get into this further, perhaps you want to reconsider
whether you really want to throw away all modifications made to the
database between the time when you break your DRBD pair, and the point
where you pull your app back up on the updated host. It seems like
you're trying to minimize down time for the price of throwing away data,
and that doesn't seem like a sound move to me. If I am understanding
your planned approach correctly, that is. If I'm not, please clarify.

Just my €.02.


: Florian G. Haas
: LINBIT Information Technologies GmbH
: Vivenotgasse 48, A-1120 Vienna, Austria

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