I'm not entirely sure I'd write it off as non production ready, you just
have to be really, really careful about setting it up. With mogilefs
just having a master<->master setup and caching paths outside of the
tracker will let you scale past anything I've built.
For HA it should still be fine... an HA VIP actually works okay. It'd be
even better if an internal mechanism could help it along, but it does
fine with minimal loss.
I think we'll be adding more internal memcached usage (and some other
stuff I don't feel comfy addmitting to co-designing yet) which will
reduce the database load a ton further. So, eh? If you're really blowing
it up please ping the list and we can discuss partitioning.
-Dormando
Tomas Doran wrote:
On Wed, 2008-04-09 at 16:05 -0700, J. Shirley wrote:
Just out of curiosity, have any production installations attempted to
run on a MySQL Cluster (NDB Cluster)? It seems like a slightly safer
method for scaling upwards without having to deal with a 3rd party HA
VIP setup.
Don't do it - it's a good idea but not production ready, and it's
failure modes are abysmal. My last company made this mistake with the
metadata for their cache subsystem (the actual cache items are in
memcache), and regretted it - they're now using 4 boxes running InnoDB
(no replication) with the data sharded across the 4 boxen. As this is a
cache system - they can lose chunks of data and that's ok(ish - there is
handling for it falling over that was built as ndb kept falling over) ;)
Some of the bad things, in quick form:
* When it crashes, it *all* crashes. Crashing it is easy - have 2
connections truncate the same table at the same time.
* Restarting a crashed cluster takes *AGES*.
* If you can deal with data loss then re-initing the cluster is much
quicker. But when you bring it back up, it will fall over - 3/4 threads
all saying SELECT stuff FROM non_existent_table will bring the cluster
to it's knees, so you'll never be able to recreate your tables.
* Unless your dataset is static, then you're doomed - it never frees
memory from deleted rows - the only way to free dead rows is to truncate
a table.
Cheers
Tom
