[Beowulf] MySQL clustering

Andrew Piskorski atp at piskorski.com
Fri Jan 16 14:38:20 EST 2004


> Date: Fri, 16 Jan 2004 16:43:33 +0000 (GMT)
> From: Guy Coates <gmpc at sanger.ac.uk>

> >quality DB.  Note that this is NOT such a rant -- I use mysql myself for
> >a small DB-driven php website, but note the key word: "small".

> Mysql4 may not be fully Ansi SQL compliant, but it is fast, which if you
> have 1000 nodes of cluster blatting results back into it, may be a more
> critical requirement.

>From what I've read, MySQL is only fast under conditions of no or low
concurrency.  Get up above 5 or so concurrent users, and performance
starts going into the toilet very fast due to table lock contention.
Note that 5 concurrent users is a trivial number for any large public
website.

SourceForge switched from MySQL to PostgreSQL a while back (two years
ago?) for exactly that reason, and had some nice little articles about
it at the time, showing the scaling graphs of both databases running
the actual SourceForge software, etc.  Better databases (Oracle,
PostgreSQL, Firebird, DB2, Sybase, MS SQL Server, etc. etc.),
particularly those using MVCC, will scale well to much higher numbers
of concurrent users.

If you don't need ACIDity, much concurrency, or powerful "real RDBMS"
style features, then MySQL may be a good choice.  And there are plenty
of applications that either fit that, or are maybe close enough.

Of course I might argue that even for most of those applications,
there are likely still better choices than MySQL, but as I've never
actually built such a maybe-MySQL-would-be-ok app, I've never had any
reason to make a real investigation into the different options there.
[shrug] YMMV.

-- 
Andrew Piskorski <atp at piskorski.com>
http://www.piskorski.com/
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