[Linux-cluster] mysql and redhat cluster suite?

Brenton Rothchild brentonr at dorm.org
Fri Dec 16 14:50:10 UTC 2005

Anyone feel free to correct me, but I was just doing some
reading on active-active MySQL + GFS last night, and
I think such an arrangement might be possible to a degree.

 From what I can read in the MySQL documentation,

MySQL can use external file locking via flock() calls,
although the 4.1 page describes that file locking is turned off
by default "because Linux file locking is not yet safe" via
a compile-time option "--skip-external-locking".

The 5.0 page doesn't warn against using external file locking
to that degree, but the option to use locking is still
disabled via the "--skip-external-locking" flag.

There are also some caveats to using the --external-locking option
in MySQL.  See the documentation for "--external-locking" in

Now, on the GFS side, locking via flock() and fcntl()-based
locks appear to be supported cluster-wide from this thread,

So, putting them together, if GFS supports file locking,
and MySQL can use file locking to support multiple instances
accessing the same files, an active-active MySQL set up should work.

I, too, and using a test cluster with GFS + iSCSI at this point,
and I plan to test MySQL 4.x and 5.x versions on it soon to
see what happens.  I really hope it works out under the loads
we want to test. :)

Like I said, anyone else feel free to correct me - I'm still
just getting started with RHCS/GFS/etc. at this point.

-Brenton Rothchild

Omer Faruk Sen wrote:
> Hi,
> I want to install a mysql cluster. But I want to ask which path do I have
> to follow? Or there is any special precautions that I have to take care
> before and after installing mysql and redhat cluster suite.
> My first impression is to install 2 node cluster it is better for me to
> use GFS and a iscsi solution for a cheaper solution. But I have understood
> from my readings that I can't setup an active-active mysql cluster using
> redhat cluster + GFS. Because one node must be locked for writing. Thus I
> think installing the second server for writing may be just for
> availability not for combining 2 machines power ( I mean using
> active-acvtive).
> Then I think to install 2 machines for write (one is standby) on a redhat
> cluster using GFS on a ISCSI system and adding a number of machines that
> use the same GFS partition for msqyl read operations is what I have to
> follow .. right?
> PS: By the way can you give me an URL that details mysql and redhat
> cluster + gfs installation? Or is there any ?

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