Jamin,
A RecoveryLog is not recommended but mandatory if you want to recover
from failures and add new nodes on-the-fly.
The recovery log can be stored in an embedded database in the recovery
log or a standalone database. To prevent the controller from being a
single point of failure (SPOF) you need a second controller. Each
controller has its own recovery log, so that the recovery log is not a
SPOF either.
You will have to define a distributed virtual database to synchronize
activities between controllers and resynchronize recovery logs. More
details in the Sequoia documentation.
Next step ... configuring the group communication! ;-)
Emmanuel
I'm having trouble wrapping my head around some aspects of the Sequoia
configuration and was hoping that someone here might be able to assist
in shedding some light on things.
First, my goal. I'm attempting to setup a fully redundant and easily
recoverable database cluster. Current implementation and testing is
based around MySQL.
I've successfully defined a single controller (eventually I will want
to increase this) with a virtual database consisting of two nodes.
Updates are propagated to both servers and queries work properly.
This lead me to test dropping a node, which appears to have worked
well. Updates and queries continued to work against the remaining nodes.
In investigating how to bring the failed node back into the cluster I
arrived at my conceptual problem. From what I can tell, in order to
ease the restoration of a failed node a RecoveryLog is needed or at
least highly recommended. However, this is itself stored in a
database, which brings us back to the initial problem with database
redundancy.
The documentation indicates that the RecoveryLog database definition
could be pointed back to a Sequoia controller (even the self same
controller). Wouldn't this then lead me back to needing a RecoveryLog
for the new RecoveryLog virtual database? Or is there some
configuration that I'm not currently grasping?
--
Emmanuel Cecchet - Research scientist
EPFL - LABOS/DSLAB - IN.N 317
Phone: +41-21-693-7558
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