On 10/9/2014 11:57 AM, Jason T. Slack-Moehrle wrote:
​Just to clarify. What state is the slave in?
If master goes down, how does the slave become active? Just reboot it and
let it come up? The wording "slave copy can't be mounted until drdb is
stopped" leads me to believe the slave is in some alternate state to be
receiving the blocks of data.
the slave is up and running, but the file systems you're replicating are
unmounted, and its services are stopped, so you could consider this to
be a 'standby' state.
yes, to use drbd, its important that you put your email spools,
databases, etc, on dedicated file system(s), NOT on the OS root file
system. I generally use lvm for all this.
a cluster management package, such as the ones suggested by another
poster, would take care of all this for you (once you have things setup
properly), if the master fails, it would 'activate' the slave, switch
its IP[*] over to be the 'production' system, and mount its file
systems, starting its services (mysqld, postfix, etc) per your
configuration.
[*] typically, you use THREE IP addresses for a HA cluster. a unique
IP for each system, used only for management, and a 'service' IP used
for the production accesses, which is held by the currently active
system. when the master fails, the slave adopts this service IP.
--
john r pierce 37N 122W
somewhere on the middle of the left coast
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