TempoDB’s timely DBaaS for the Internet of Things. ScaleBase 2.0. And more

For 451 Research clients: TempoDB has timely database service for the Internet of Things bit.ly/YcQuqA

— Matt Aslett (@maslett) February 13, 2013

For 451 Research clients: ScaleBase provides centralized management of distributed MySQL databases bit.ly/YcQTcs

— Matt Aslett (@maslett) February 13, 2013

For 451 Research clients: XtremeData turns its attention to cloud-based data warehousing bit.ly/XB7MLY

— Matt Aslett (@maslett)

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There have been a number of comments that Amazon RDS does not allow users access to MySQL replication capabilities (for example here and here).  This is a pity. Replication is one of the great strengths of MySQL and the lack of it is a show-stopper for many users.  As of the latest build of Tungsten Replicator half of this problem is on the way to being solved. You can now set up real-time replication from an external MySQL master into an Amazon RDS instance.

In the remainder of this article I will explain how to set up Tungsten replication to an Amazon RDS slave, then add a

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RDS has created some basic tooling for looking at the internal status variables within MySQL called Global Status History or "GoSH" though unfortunately the tooling is broken.

The tooling, detailed at the following link here is meant to snapshot the output of "show status" and squirt the data into a table in the MySQL schema called mysql.rds_global_status_history.

The issue is that the bootstrapped event called 'ev_rds_gsh_collector' is missing and therefore the procedures to enable the snapshotting fail.

It appears that whenever an RDS instance is started (or bounced) the contents of the 'mysql' schema is re-created - therefore the injection of the row into the event table is missing from whatever init script AWS has.





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RDS instance details

• sysbench seeded 100Gb database and then snapshotted
• 1Tb of RDS storage for the database
• RDS MySQL 5.5.27
• Default my.cnf RDS configuration except (find the full 'show global variables' output at the end of this post)
• performance_schema is enabled
• innodb_flush_logs_at_trx_commit = 0
• provisioning an RDS instance for each instance size / PIOPS configuration from the seeded database. (10 in total) 

Test details

• Amazon RDS 
• Within an AWS VPC
• US-East

First warm up innodb by running sysbench with options

• oltp table size 1000000000
• max-requests 0
• max-time 300 (5 minute warm up)
• oltp test mode complex
• oltp index updates 10
• oltp user delay

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I recently came across a dev VM running MySQL 5.0.77 (an old release, 28 January 2009) that didn’t have InnoDB available. skip-innodb wasn’t set, SHOW VARIABLES LIKE '%innodb%' looked as expected, but with one exception: the value of have-innodb was DISABLED.

I confirmed this with SHOW ENGINES:

(root@localhost) [(none)]> show engines;
+------------+----------+----------------------------------------------------------------+
| Engine     | Support  | Comment                                                        |
+------------+----------+----------------------------------------------------------------+
| MyISAM     | DEFAULT  | Default engine as of MySQL 3.23 with great performance

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My list of reasons for never using or recommending Amazon’s MySQL RDS service grows every time I experience problems with customers. This was an interesting and still unresolved issue.

ERROR 126 (HY000): Incorrect key file for table '/rdsdbdata/tmp/#sql_5b7_1.MYI'; try to repair it

You may see this is a MyISAM table. The MySQL database is version 5.5, all InnoDB tables and is very small 100MB in total size.
What is happening is that MySQL is generating a temporary table, and this table is being written to disk. I am unable to change the code to improve the query causing this disk I/O.

What I can not understand and have no ability to diagnose is why this error occurs sometimes and generally when the database is under additional system load. With RDS you have no visibility of the server running the production database. While you have SQL

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The attached storage used by Amazon’s managed Relational Database Service has a known issue where the bytes per inode ratio is very high (default on RHEL5 systems is 4096, to be found in /etc/mke2fs.conf). Amazon does not allow any administrative access to these instances so there is no way to reformat the filesystem to allocate more inodes, or attach storage the user can format with a different ratio.

This becomes problematic for databases that have many small tables (generally MyISAM tables, or InnoDB with the innodb_file_per_table setting) which quickly consume the available inodes. When the inode allocation is exhausted MySQL responds with

"ERROR 1030 (HY000): Got

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Amazon’s SimpleDB isn’t a relational database, but it does provide elastic scalability and high-availability. Amazon’s recently announced Relational Database Services (RDS) is a relational database, but it doesn’t provide elastic scalability or high-availability. If you are deploying enterprise applications on the cloud (including Amazon Web Services), you might want to look at ScaleDB because it is a relational database and it does provide elastic scalability and high-availability.

Amazon describes SimpleDB by comparing it to a clustered database:

"A traditional, clustered relational database requires a sizable upfront capital outlay, is complex to design, and often requires extensive and repetitive database administration. Amazon SimpleDB is dramatically simpler, requiring no schema, automatically indexing your data and providing a simple API for storage and access.

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Amazon’s SimpleDB isn’t a relational database, but it does provide elastic scalability and high-availability. Amazon’s recently announced Relational Database Services (RDS) is a relational database, but it doesn’t provide elastic scalability or high-availability. If you are deploying enterprise applications on the cloud (including Amazon Web Services), you might want to look at ScaleDB because it is a relational database and it does provide elastic scalability and high-availability.

Amazon describes SimpleDB by comparing it to a clustered database:

"A traditional, clustered relational database requires a sizable upfront capital outlay, is complex to design, and often requires extensive and repetitive database administration. Amazon SimpleDB is dramatically simpler, requiring no schema, automatically indexing your

  [Read more...]