[mythtv-users] The purpose of a Secondary Backend is... (is this really OT? I'm not sure)

Sam Hooker mythtv at noiseplant.com
Fri Jun 20 13:19:22 UTC 2008

Hash: SHA1

Sam Hooker wrote:
| Well, assuming your master backend and network can handle the extra
| load, you could use Heartbeat (Linux-HA) with DRBD[1] to have a passive
| replicant of your master backend. Maybe on a beater (but still capable
| of playing your HDTV-grade recordings) laptop, so it would  be truly
| portable: as soon as you yanked the network cable to take the portable

OK, upon reflection: configuring this with Heartbeat would cause the
instance on the master backed to shut down the services and unmount the
disk. Probably not what you want, eh? ;-)

You COULD still use DRBD by itself (to replicate the on-disk storage)
with MySQL replication for the database. In this case, "pulling the
plug" and severing the connection between the master backend and your
portable would cause EACH machine to think that the other had gone dead,
and mount the replicated disk.

This would, necessarily, induce a situation called "split brain" (or
"cluster partition") but you probably wouldn't care (as your reasons for
doing this at all would be less related to high availability), and DRBD
makes it easy to recover from split brain[1] when you bring your
portable back home. In any case, it wouldn't affect your ability to play
the recordings while your portable is disconnected from the master.

So, sorry for initially suggesting a silly scenario. This one, however,
would probably work just fine. :-D


- -sth

[1] http://www.drbd.org/users-guide/s-resolve-split-brain.html

sam hooker|mythtv at noiseplant.com|http://www.noiseplant.com

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