Hi,<br><br><div class="gmail_quote">On Wed, Mar 30, 2011 at 12:37 AM, Mateusz Kalisiak <span dir="ltr"><<a href="mailto:mk.spare999@gmail.com">mk.spare999@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Hello Everyone,<br><br>I'd like to setup the standard MySQL-DRBD-HA architecture:<br>- PRIMARY server with MySQL and mounted /dev/drbd0,<br>- SECONDARY just being standalone and waiting for failover.<br>Additionally, during normal cluster activity (primary server is fine and active) I'd like to perform backup of MySQL data, but using only SECONDARY node.<br>
Did anyone tried such thing? <br></blockquote><div><br></div><div>If it's an actual HA architecture, the primary node is the only place where read/write operations are possible. On the secondary node, you cannot mount the /dev/drbd0, not even as read-only. If you search a little bit on the archives, you'll see why mounting the drbd device on the secondary node as read-only has bad consequences as well.</div>
<div><br></div><div>An MySQL Active-Active setup _might_ seem like a good idea for the case you want to achieve, but the implementation behind the idea, to keep it all working as expected is troublesome to say the least. The replication channels on the Active-Active MySQL setup need to be redundant, and when one replication channel fails there is no automatic recovery for it. So a resource agent that knows how to handle this type of behavior is required.</div>
<div><br></div><div>Then with the Active-Active setup, on the storage level, you need a dual-primary setup. That involves a cluster filesystem with a distributed locking manager to prevent concurrent access to the same data. Also being an Active-Active setup, and assuming that the frontend is only trying to connect to one of the instances of the MySQL database (no load balancing), then extra care must be taken with the VirtualIP assignment to the proper (primary) node since both nodes will run the same resource (MySQL) at the same time. </div>
<div><br></div><div>When all of the above are met, then and only then will you be able to perform a backup on the secondary node.</div><div><br></div><div>Another option would be to have a second MySQL resource run in a Slave mode (read-only) and have it run always on the secondary node.</div>
<div><br></div><div>So node1 is primary, it holds MySQL Master (read-write), node 2 is secondary, holds MySQL Slave (read-only). Primary node replicates MySQL Master read/write data to secondary. Secondary node replicates MySQL Slave read-only data to primary. Thus you can always perform the backup from the secondary node.</div>
<div>--------------------------------------------------------------</div><div>Primary ---------------------------------Secondary</div><div>--------------------------------------------------------------</div><div>MySQL---->---replication----->----MySQL</div>
<div>Master Master</div><div>--------------------------------------------------------------</div><div>MySQL----<---replication-----<----MySQL</div><div>Slave Slave</div>
<div>--------------------------------------------------------------</div><div><br></div><div>Regards,</div><div>Dan</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Maybe such feature would be available somehow in ACTIVE-ACTIVE architecture (although according to MySQL docs it's not <a href="http://dev.mysql.com/doc/refman/5.0/en/drbd-architecture.html#qandaitem-B-14-3-1-1" target="_blank">http://dev.mysql.com/doc/refman/5.0/en/drbd-architecture.html#qandaitem-B-14-3-1-1</a> )<br>
<br>Regards,<br><font color="#888888">Mateusz<br><br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>Dan Frincu<div>CCNA, RHCE</div><br>