Wednesday, July 18, 2007


I am evaluating database clustering solutions. At the moment I am reading the MySQL documentation. I'm very skeptical but hey, I want to give it a fair chance.

The more I read though, the scarier it looks. Here are some of the "unsupported or missing features":

# Foreign key constraints. The foreign key construct is ignored, just as it is in MyISAM tables.
# Savepoints and rollbacks. Savepoints and rollbacks to savepoints are ignored as in MyISAM.
# Durability of commits. Commits are replicated, but there is no guarantee that logs are flushed to disk on commit.

On other pages we have such gems as:

# Online adding or dropping of data nodes is not currently possible. In such cases, the entire cluster must be restarted.

But they also claim MySQL gives you "99.999%" uptime, or "five 9s" uptime. How they arrived at this number is beyond me, especially if you can't add nodes (what if one machine dies and you need to replace it?).

Like I said...yikes.

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