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Previous 30 Newer Entries Showing entries 31 to 60 of 61 Next 1 Older Entries

Displaying posts with tag: Technical (reset)

MySQL Stored procedure – Execute query if table or Column exists
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Well procedures mainly carried out working with information schema and it’s usage in stored procedure. Procedures are fairly simple and easy to understand. 1. Edit_table – following procedure executes queries to […]
Stored procedure to Find database objects
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This procedure lists available database objects under passed database name. It lists present Tables, Views, Stored Procedures, Functions and Triggers under particular database. It also lists storage engine of tables. […]
MySQL master master replication monitor with php code
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For monitoring replication we know a lot of tools and codes – but this one is different because I wrote it Well this is fairly simple php code for monitoring […]
Calculate Mysql Memory Usage – Quick Stored Proc
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While going through mysql doc and MySQL Server Memory Usage, I noted following quick points regarding how mysql uses memory. We have global buffers which are allocated irrespective of connections […]
Scheduled Backup MySQL Administrator & Windows Scheduler – Odd
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Creating scheduled backup using administrator is an easy task. Follow the GUI and you’re done. But I observed something different! MySQL Version: 5.0.83 Community MySQL Administrator: 1.2.17 Machine: Intel P4, […]
Monitor multiple mysql replication using php: Updated
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Monitoring a replication is an important aspect. As replication includes multiple nodes, it is essential to track activity and status across all mysql servers involved in replication. To monitor replication […]
Quick Multi MySQL Server Installation with Master-Master Replication on Same Windows Box
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This article is a brief step-by-step tutorial on the subject task which is divided into the following main parts: Installing two MySQL Server Instances Setting up master-slave replication Setting up […]
Replication slave lag monitoring using heartbeat and windows batch scripts
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“Show Slave Status” command has a last column “Seconds_Behind_Master”, which gives us idea about how much time slave is lagging behind master. It is an important to be considered parameter […]
Search / find through all databases, tables, columns in MySQL
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What will you do if one day some one ask you to find single string in all databases, all tables and in all columns? I just read such question and tried to find […]
Problem with Master Master Replication and Auto Increment
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Consider we’ve already set a master-master replication. Now create following table on Server1: CREATE TABLE `temp` ( `id` int(10) NOT NULL auto_increment, PRIMARY KEY (`id`) ) ENGINE=MyISAM AUTO_INCREMENT=12 DEFAULT CHARSET=latin1; […]
Internal metadata, and why we recommend it
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One of the things that repeatedly seem to puzzle users about the DRBD is the question of whether to use internal or external metadata. Remember, DRBD sets aside a small area on a local disk (on every cluster node) where it keeps the Activity Log, the quick-sync bitmap, data generation UUIDs, and a few other bits and pieces for local housekeeping.

The specific aspect that is to be discussed here is the Activity Log. Without going into too much detail, let’s be satisfied with the factoid that DRBD

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My love affair with MySQL Cluster (contains benchmark stories)
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As someone may have noticed, I recently wrote a trilogy on how to dive into the MySQL Cluster source code. Unfortunately my overtures towards the MySQL Cluster source code ended up being only a look-but-don't-touch affair, as I failed to actually get to touch her internals with my text editor. Even so, in this post I'd like to tell about the background to my love affair with this beauty, by relating to some benchmarks I've been working on together with my customers.

Oh, and I'd like to apologize already, that I cannot mention where these benchmarks were done, what the schema looked like and the exact numbers. If you want that kind of real benchmarks, you should read Mikael's blog, or watch the slides from this webinar

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Look mom, no hands: I can fix MySQL Cluster bugs by just staring at them (part III)
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(Continued from part II where I tried to fix a bug and found out that the affected part of the code had been rewritten, so the bug didn't exist anymore.)

Magnus gives a helpful hint...

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Actually trying to do something techical, part II: HowTo fix a MySQL Cluster bug without touching a single line of code!
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This is part II of my efforts to prove myself that I can do programming. In part one I successfully created a MySQL Cluster branch for myself and compiled it.

Let's go to the public MySQL bug database and see if there are any trivial MySQL Cluster bugs I could sharpen my teeth on. Heh, sure enough #32658 looks simple enough. There is a typo in an output string - so I could fix that without even doing any C++ code! (Funnily, a MySQL internal comment to the bug says something about it being embarrassing. Guess it is a good bug for me then, as patching over embarrasments is what Sales Engineers do routinely :-)

Let me see...

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Actually trying to do something techical: branch a MySQL Cluster bzr repository - part 1, branch and build
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My collagues Anders and even Ivan sometimes blog about the grandeur of being a Sales Engineer. And I agree, it is a great job, probably the best I ever had, so far. But let me share a secret: It's not as technical as you'd think. Sure, they call me a "pre-sales consultant" alright, but I would be ashamed of comparing my own work with those of the real consultants. I sometimes jokingly say that the most amazing technical things in my job are airplanes (they fly in the air!) and how to make a nice slideshow. (OpenOffice Impress sucks btw, and I always envy my OS X + Keynote using friends on this one

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A few seats still left in DRBD Total on-line training
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By popular demand, we are now offering an on-line incarnation of our DRBD Total training sessions, normally taught in a 4-day on-site course. The next such training commences on May 18 (next Monday), and we still have a few seats left — so if you’re interested, grab one while you still can!

What’s covered in this course?

Here is an overview of the course highlights:

  • Introduction to High Availability Clustering & DRBD
  • Setting up a DRBD resource and common failure scenarios
  • Configuring and running the Heartbeat/Pacemaker cluster stack
  • Highly available NFS, MySQL, and virtualization
  • DRBD performance tuning and optimization
  • DRBD integration with Red Hat Cluster Suite
  • Recent and future DRBD development

Every course attendee gets a virtual

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Upload Image to MySQL using PHP
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Upload Image to MySQL using PHP As a new-bie to php/mysql, I tried different stuffs. So here I’m with my php code for Image Upload to MySQL. Its a quite […]
Difference MyISAM and InnoDB Storage Engines Mysql
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MyISAM InnoDB Default since version 3.23 Relatively newer Files storage: FRM: table definition, MYD: Actual Data MYI: Index File FRM: table definition .ibd file (concept of table space) or single […]
Choosing between MyISAM and INNODB – MySQL Storage Engines
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After reading at a lot of places for the the single repeatative question, “What engine shall I choose – MyISAM or Innodb?”, this is what I’ve got. Following are points […]
Using MySQLTuner – MySQL Optimization Tool
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MySQLTuner is a script written in Perl that will assist you with your MySQL configuration and make recommendations for increased performance and stability. Within seconds, it will display statistics about […]
Perl Script for Analyze – Optimize – Repair Mysql Databases
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The perl script is mainly created to avoid manual Mysql Server Maintenance. The script uses Perl module DBI. You need to provide access credentials and database name(optional). Regarding Analyse, Optimize […]
DRBD for Dolphin Express Webinar
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As part of our partnership with Dolphin Interconnect Solutions, we are presenting two webinars on DRBD for Dolphin Express on Nov. 5 (European business hours) and Nov. 12 (American business hours).

Both DRBD and Dolphin Express already being a fixture in the MySQL (http://www.mysql.com) universe, this webinar should be particularly interesting to those of you who want to minimize database write latency while maintaining fully redundant and transaction-safe high availability. However, it’s also a must see for virtualization and mail service DRBD users, who also typically have a need for low latency.

This is, of


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Public draft of DRBD Users’ Guide released
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A public draft version of the all-new DRBD Users’ Guide has just been released. Feedback is more than welcome.

You may want to read the announcement as well.


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DRBD 8.2.3 released; boasts online device verification, CPU affinity optimization
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DRBD 8.2.3 was released today. Even though just a micro release in terms of version numbering, it comes with a couple of very handy brand new features: on-line device verification, and tunable processor affinity.
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Step-by-step upgrade from DRBD 0.7 to DRBD 8
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I’ve been asked by a number of people on how to do an upgrade from DRBD version 0.7 to DRBD 8. This upgrade does necessitate some minimal service down time, but it’s really not rocket science. And no, it does not force you to sync all of your data all over again.

Here’s my quick write-up.

An initial word of caution

Do not, I repeat do not attempt your upgrade unless you have at least read this blog entry to the finish.

Getting ready

First, you need to make sure that you have both your DRBD 8 userland binaries and kernel module ready to install. For our support customers, this means that you simply download two RPMs (or .debs) from our support web site. Make sure you have the right packages; you want those that match your system architecture and (for the kernel module) also your running


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An underrated cluster admin’s companion: dopd
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Split brain, with DRBD, is much less of a disaster than in conventional cluster setups employing shared storage. But, you ask, how can I protect my DRBD cluster against split brain in the first place? Here’s how.

Let’s briefly reiterate what split brain, in the DRBD sense, really means. DRBD split brain occurs when your nodes have lost their replication link due to network failure, and you make both nodes Primary after that.

When just the replication link dies, Heartbeat as the cluster manager will still be able to “see” the peer node via an alternate communication path (which you hopefully have configured, see this post). Thus, there is nothing that would keep Heartbeat from migrating resources to that DRBD-wise disconnected node if it so decides


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DRBD 8.2.0 introduces protocol integrity checksums
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DRBD 8.2.0, released today, includes a much requested new feature, embodied in the new data-integrity-alg configuration option: DRBD protocol level data integrity checksums.

A few months ago, some users alerted us to DRBD replication issues where DRBD supposedly “ate their data”, i.e. corrupted replicated data in transit. Eventually we traced those problems not to DRBD errors, but in fact to network drivers messing up TCP checksums or segmentation. Typically this was related to using either TCP segmentation offloading (TSO) or TCP checksum offloading. However, at the time DRBD had no way of detecting these errors — you would only find out if you switched over to your Secondary, only to find your data not having been replicated properly.

With DRBD 8.2.0, you


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Performance tuning DRBD setups
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These days, we seem to be getting a lot of inquiries from new or would-be DRBD adopters, especially MySQL (http://www.mysql.com" target="_blank) and PostgreSQL DBAs wanting to add high availability to their master database servers. And these, unsurprisingly, turn out to be two of their most popular questions:

How will using DRBD affect my write performance?

… and …

What are DRBD’s most important tunables with regard to write performance?

Let’s take a look at both of these issues. Ready? Let’s go.

Basically, there’s usually one important potential bottleneck in any DRBD “Protocol C” (synchronous replication) setup, and it’s not the network connection. With ubiquitous Gigabit


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Why DRBD won?t let you mount the Secondary
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As I’m sure you’re aware, DRBD disallows access (any access, including read-only) to a DRBD device in Secondary mode. This always raises questions like the one I’ve taken the liberty to quote here. It came up in a MySQL webinar (http://www.mysql.com/news-and-events/on-demand-webinars/" target="_blank) on replication and HA:

Because of the asynchronous nature of [MySQL] replication we end up with a dilemma when looking at using slaves as read nodes in that the only time we go to the database for information is to build a local cache file, and that local cache file is ONLY removed when information related to that cache file changes, it is NOT based on time. If we had a synchronous method of replication we would then know the cache files


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Using DRBD directly (without a file system)
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Some applications require direct access to a block device, without an intermediate file system. Some Oracle and MySQL configurations are an example, as are some Xen setups, or IET. Can you do this with DRBD? Sure you can.

However, you need to fulfill two prerequisites:

  • Your application can’t access DRBD while it’s in the Secondary role. So, you must make sure DRBD is Primary before your application attempts using that device.
  • The user in whose context your application runs needs read/write access to that device.
  • Your cluster manager, when configured properly, normally takes care of item #1 for you. #2 is a little trickier:
    Normally, DRBD’s device nodes are owned by root:disk, with permission bits set to 0660 (rw-rw----). So in order to allow your

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    Previous 30 Newer Entries Showing entries 31 to 60 of 61 Next 1 Older Entries

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