On Dec 11, 2007, at 11:29 AM, Matt Shields wrote:
On Dec 11, 2007 1:39 PM, J. Potter <jpotter-centos@xxxxxxxxxxxxx>
wrote:
... But I saw a presentation at the Boston MySQL Meetup.com
group about how to do master-master in mysql 5. We're about to
implement this in the next few weeks. ...
I've run into issues with crash recovery in master-master mode:
- master A is at position X
- master B, replicating from A, gets to position X
- master A syncs to its filesystem that it's at position X
- master A receives some inserts, and is now at position Y
- master B, replicating from A, gets to position Y
- master A crashes before the position gets synced to filesystem
- master A gets rebooted, recovers from innodb log, but has itself
only marked at position X
- master B requests position Y from master A, but that position
doesn't exist yet, so replication breaks.
Perhaps someone here knows the proper recovery procedure at this
point?
If this were master-slave, I'd probably do an LVM Snapshot and get a
fresh copy of the master db. The same could be done for
master-master.
The problem is you'll have some inconsistency between your master A's
view of the database and the master B's view. You lose any changes to
the data on master B. It would be nice to be able to merge any changes
from B that hadn't made their way to master A yet. At that point
you're examining binlogs.
Ryan
--
Ryan Ordway E-mail: rordway@xxxxxxxxxxxxxxx
Unix Systems Administrator rordway@xxxxxxxxxxxxxxxxxxxxxxx
OSU Libraries, Corvallis, OR 97331 Office: Valley Library #4657
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