Toward strict consistency in distributed databases

July is vacation time in Finland. Which means it is a great time to read blogs and papers on consistency in distributed databases! This and following blogs are my reading notes and thoughts. Mostly for my own benefit but if you benefit too, that's great. Note also that my ambition is not to appear like an authority on consistency. I just write down questions I had and things I learned. If you have comments, feel free to write some below. That's part of the point of blogging this!

20 years later, what's left of the CAP theorem?

The CAP theorem was published in (party like it's...) 1999: Fox Armando, Brewer Eric A: Harvest, Yield, and Scalable Tolerant Systems.

Since its publication it has provided a beacon and rallying cry around which web scale distributed databases could be built and debated. It(s interpretation) has also evolved. Quite quickly the original 1999 formulation was abandoned, and from there it has further eroded as real world database implementations have provided ever more finer grained trade offs for navigating the space that - after all - was correctly mapped out by the CAP theorem.

Pick ANY two? Really?

Presentation: Databases and the Cloud (and why it is more difficult for databases)

A week ago I again had the pleasure to give a guest lecture at Tampere University of Technology. I've visited them the first time when I worked as MySQL pre-sales in Sun.

To be trendy, I of course had to talk about the cloud. It turns out every section has the subtitle "...and why it is more difficult for databases". I also rightfully claim to have invented the NoSQL key-value development model in 2005.

The different ways of doing HA in MySQL

A week ago Baron wrote a blog post which can only be described as the final nail in the coffin for MMM. At MySQL AB we never used or recommended MMM as a High Availability solution. I never really asked about details about that, but surely one reason was that it is based on using the MySQL replication. At MySQL/Sun we recommended against asynchronous replication as a HA solution so that was the end of it as far as MMM was concerned. Instead we recommended DRBD, shared disk or MySQL Cluster based solutions. Of course, to replicate across continents (geographical redundancy) you will mostly just use asynchronous replication, also MySQL Cluster used the standard MySQL replication for that purpose.

A database for everyone (comments on Sybase acquisition)

One thing I haven't seen anybody commenting on is the fact that with SAP acquiring Sybase, it will be the last major independent database company to be merged into a larger SW company. (To say this, you can qualify MySQL AB as a major database company, but disqualify, say, EnterpriseDB or InterBase, which imho is entirely reasonable.)

Analyst reports on database market share in SMB segment? Anyone?

Has anyone read the report Microsoft, IBM and Oracle Lead the SMB and Mid-Market Database Segment - Yankee Group - 7/31/2006 - 5 Pages - ID: YANL1327246?

Paying 800USD just to know the percentages of each database is a bit expensive for my small startup budget, especially since it is not me who needs the information.

Back from MySQL User Conference

I thought I had already conquered the jet lag last night when I fell asleep at 22:00 (that's 10 pm...). But then I woke up somewhere around 2:30, read a book for a while until I decided to give up and have a nice breakfast. I kind of like jet lag though, it is a nice feeling to get out of bed 5:30, when no one else is awake, and birds are singing outside.

There would be a lot to tell about the conference, but you kind of find summaries from many live bloggers on Planet MySQL. One interesting aspect of the conference of course was to meet so many interesting people, many of whom I work with of course, but meeting them in flesh is still great. And Santa Clara being in Silicon Valley adds another funny revelational feeling to it all. For a European Yahoo, Google, Digg and others are Internet companies and seeing that they actually do have tangible offices in Silicon Valley was a surprisingly unreal revelation to me. Oh yes, I also saw the Transmeta offices, you know, where Linus went to work after graduating with the M.Sc. work titled "Linux: A portable operating system" (What did YOU do for master's thesis? I know I did multiple choice quizzes, I'm not kidding...). And when strolling in Santa Clara I was also amused to find out that apparently Freedom also begins there, just a few blocks away from where the conference was held!

Road sign says "Begin Freedom CIR"


I was wrong in my last post, it seems that all Sun database developers are now part of the same organisation, including PostgreSQL's Josh Berkus.

MySQL has the pluggable storage engine architecture, which is unique in the industry. The idea is you pick from among a suite of storage engines the most suitable one. PostgreSQL on the other hand has a plugin architecture for programming languages you can then use for stored procedures. And the cool thing about Open Source...

Someone went as far as to implement a PostgreSQL plugin of LOLCODE, a funny programming language I didn't know about until recently. So now you could do this with PostgreSQL:

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