Master-Master Replication

Creating and maintaining a duplicate copy of a database or file system on a different computer, typically a server.  The term usually implies the intelligent copying of parts of the source database which have changed since the last replication with the destination.

Replication may be one-way or two-way.  Two-way replication is much more complicated because of the possibility that a replicated object may have been updated differently in the two locations in which case some method is needed to reconcile the different versions.

We have seen how the one-way replication works i.e. Master-Slave; here whatever changes are updated on the Master server is replicated onto the Slave server.

Two-way replication i.e. Master-Master replication will be bit different. As the name itself suggests both the servers will be Master to another.

Master-Master replication allows data in …

Very helpful when you need some quick export of a small set of tables and/or data in tables: export SQL dump directly to clipboard, so you can paste it either in a query tab or elsewhere. Implemented in r3206.



Thanks to akrueger for this suggestion!

Most software people are aware of the ACID acronym coined by Jim Gray. With the growth of the web and open source, the scaling and complexity constraints imposed on DBMS implementations supporting ACID are more visible, and new (or at least new terms for known) compromises and tradeoffs are being discussed widely. The better known NoSQL systems are giving insight by example into particular choices of tradeoffs.

Working at MySQL, I have often been surprised at the variety of potential alternatives when implementing a DBMS, and the number of applications which don't need the full set of ACID letters in the strictest form. The original MySQL storage engine, MyISAM is one of the first and most successful examples of an 'ACID remix'. The people …

At the MySQL UC 2010 (on Tuesday 4/14 11:55 am) me and my colleague Joffrey Michaie will present MySQL Cluster - Deployment Best Practices. We will give talk about what is important to think about when deploying MySQL Cluster, what to do, what not to do, operational aspects and a few other practical things.
This session will be a great follow-on to the introductory session on MySQL Cluster (and the tutorial).

After the Deployment session, same day at 2:00pm, I will also have a session on …

Q4M (Queue for MySQL) periodically performs an operation called "compaction", which is sort of a garbage collection, that collects empty space from a queue file and returns to the OS.

The pitfall that exists until now was that during compaction, all operation on the queue table was being blocked.

My opinion was (is) that it is not a serious problem for most users, since the time required for compaction will be small in most cases (the time depends on the number (and size) of the rows alive on the queue table, and the number of the rows alive will be mostly small).

But for usecases where fast response is a requirement, I have added a "queue_use_concurrent_compaction" option to Q4M in the 0.9.3 prerelease.  When the variable is set to one in my.cnf, INSERTs will not be blocked during compaction.  Another configuration variable …

Along with maximal possible fsync/sec it is interesting how different software RAID modes affects throughput on FusionIO cards.

In short conclusion, RAID10 modes really disappoint me, the detailed numbers to follow.

To get numbers I run sysbench fileio test with 16KB page size, random read and writes, 1 and 16 threads, O_DIRECT mode.

FusionIO cards are the same as in the previous experiment, as I am running XFS with nobarrier mount options.

OS is CentOS 5.3 with 2.6.18-128.1.10.el5 kernel.

For RAID modes I use:

• single card ( for baseline)
• RAID0 over 2 FusionIO cards
• RAID1 over 2 FusionIO cards
• RAID1 over 2 RAID0 partitions (4 cards in total)
• RAID0 over 2 RAID1 partitions (4 cards in total)
• special …

Berkeley DB (BDB) is undoubtedly the workhorse among the opensource embedded database engines. It started as a university project in the mid-eighties and was further developed by Sleepycat Software, until it got acquired by Oracle in February 2006.

I had the impression that BDB had lost a lot of its popularity among opensource developers to SQLite in recent times, which has evolved into becoming the default choice for developers looking for an embedded data store. I'd assume primarily because the code is not released under any particular license, but put in the public domain …

Dear Community,

It is time to announce the next version of backup software from Percona - XtraBackup 1.1.

The list of changes in version 1.1 includes:
Changelog:

• XtraBackup is built on a base of MySQL 5.1.44 with InnoDB plugin 1.0.6
• Added --host option
• tar4ibd can treat over 64GB file
• tar4ibd is default method for stream, even tar is specified
• the binary supports compressed tables and Baraccuda format

Fixed bugs:

• Bug #529874: innobackupex cannot treat exit code of xtrabackup executable
• Bug #498660: xtrabackup not handling barracuda compressed table format
• …

I got a comment from a reader about the Naive Trees section of my presentation SQL Antipatterns Strike Back. I've given this presentation at the MySQL Conference & Expo in the past.I'd also like to mention that I've developed these ideas into a new book, SQL Antipatterns: Avoiding the Pitfalls of Database Programming. The book is now available in Beta and for pre-order from Pragmatic

The binary version for MySQL Cluster 7.1.2a has now been made available at http://dev.mysql.com/downloads/cluster/ under the Development tab.

Note that this beta load contains the latest NDBINFO and MySQL Cluster Connector for Java (ClusterJ) enhancements – please try them out and provide feedback (any bugs should be reported through bugs.mysql.com.

A description of all of the changes (fixes) that have gone into MySQL Cluster 7.1.2a (compared to 7.1.1) can be found in the MySQL Cluster 7.1.2a Change Log.