On 7 Mar 2007, at 06:39, Cabbar Duzayak wrote:
I am particularly interested in master-to-master replication (not even
sure if this is possible with mysql) and/or real-world usage
scenarios/examples as to how much load it can handle, how reliable it
is, etc?
I've had some success with it.
I found these useful:
http://www.onlamp.com/pub/a/onlamp/2006/04/20/advanced-mysql-
replication.html
http://www.imvu.com/blogs/index.php?
blog=12title=using_master_master_replication_for_backmore=1c=1tb=1p
b=1
New 5.1 stuff is mentioned here:
http://firestuff.org/wordpress/2006/01/24/finally-sane-mysql-clustering/
In practice, you do need to tread carefully with circular
replication. In particular there is no transactional isolation
between servers, so when doing a transaction, it helps to make sure
all queries go to the same server within a single transaction. The
other big thing to look out for is replication latency - as far as I
can tell, transactions are not replicated until committed, but if you
have a transaction that takes a few minutes, you will have to wait
for the same time again after committing for that change to appear on
the other master. So if you do a write immediately followed by a
read, the read may be missing what was just written if the read goes
to a different server. I'm not sure if the new 5.1 stuff helps here.
You should gain the same amount of performance for reads as with a
normal master-slave setup, but write performance may be slightly
slower because of the replication overhead, and all masters have to
execute all queries anyway, so there's no benefit in distributing
writes (unlike reads).
You do get easy failover - you just point your clients at the other
server if the default master fails, no messing with reallocating
masters required. That's probably the biggest win.
To take this a step further, I've been tempted to look at
Continuent's Sequoia and libMySequoia:
http://sequoia.continuent.org/
http://www.devguy.com/bb/viewtopic.php?p=1874
http://phpthinktank.com/plugin/tag/mysql
Marcus
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Marcus Bointon
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