[DRBD-user] dual primaries and KVm

Mark Watts m.watts at eris.qinetiq.com
Wed Nov 4 10:14:41 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.

>         the idea is to use a mysql DB on these nodes,
>         right now I use mysql replication, but had a lot of trouble
>         with that,
>         also in a dual primary setup I have to only deploy and backup
>         one system.
>         Also to have nearly zero downtime when 1 node crashes, I have
>         a lot of primary/secondary setups with heartbeat.
>         Right now im just testing things out and im gratefull for
>         your/any input-
> another question that just comes up,
> when I create a drbd pair ontop of an LVM volume and now want to
> create a GFS on this drbd,
> do I realy have to create another LVM ontop of the drbd(which is ontop
> a LVM), wouldnt this confuse things?

GFS is a file system that allows two (or more) nodes to write to the set
of files at the same time. Are you planning on storing the KVM disk
images on GFS, or are you trying to run GFS within the nodes?

Putting what you have now aside for a moment, what end result are you
actually trying to achieve? A redundant database pair doesn't explicitly
need to run in KVM, or even run on GFS.

Primary/Secondary DRBD using heartbeat to mount an EXT3 file system and
manage a single instance of MySQL, is a very reliable way of achieving a
redundant database server, and neither KVM or GFS is required.

Of course, running KVM guests and storing their disk images on GFS
(Primary/Primary DRBD) is a valid way forward but its not quite clear
what you're actually aiming for.


Mark Watts BSc RHCE MBCS
Senior Systems Engineer, Managed Services Manpower
QinetiQ - Delivering customer-focused solutions
GPG Key: http://www.linux-corner.info/mwatts.gpg
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