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Re: [Linux-cluster] mysql and redhat cluster suite?



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,
http://dev.mysql.com/doc/refman/5.0/en/system.html
http://dev.mysql.com/doc/refman/4.1/en/system.html

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
http://dev.mysql.com/doc/refman/4.1/en/server-options.html
http://dev.mysql.com/doc/refman/5.0/en/server-options.html

Now, on the GFS side, locking via flock() and fcntl()-based
locks appear to be supported cluster-wide from this thread,
http://www.redhat.com/archives/linux-cluster/2004-October/msg00311.html

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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