It is a common misconception that DRBD (or any block-level data replication) solution can magically make an application crash-safe that intrinsically isn’t. Baron highlights that misconception in a recent blog post.

I want to reiterate and stress that point here: if your application can’t reliably survive a node crash, it won’t successfully fail over on a replicated (or shared, for that matter) data device. But if it can, and DRBD is replicating synchronously, then DRBD won’t break it. In other words: try pulling the power plug on your machine while your app is running, and power back on. If your application recovers to a consistent state, you’re clear. If it doesn’t, don’t bother adding DRBD until you fix that.

…

Any time you can get two for the price of one (a “2Fer”), you’re ahead of the game. By implementing our shared cache as a separate tier, you get (1) improved performance and (2) storage flexibility…a 2Fer.

What do I mean by storage flexibility? It means you can use enterprise storage, cloud storage or PC-based storage. Other shared-disk cluster databases require high-end enterprise storage like a NAS or SAN. This requirement was driven by the need for:

1. High-performance storage
2. Highly available storage
3. Multi-attach, or sharing data from a single volume of LUN across multiple nodes in the cluster.

Quite simply, you won’t see other shared-disk clustering databases using cloud storage or PC-based storage. However, the vast majority of MySQL users rely on PC-based storage, and most are not willing to pay the big bucks for high-end storage.

ScaleDB’s Cache …

Crash Safety is a big deal in the database league. Lack of durability can lead to all sorts of terrible things upon a catastrophic event. Many projects, especially in the so called NoSQL world compromises crash safety in return for higher QPS. The argument there is that the availability of the overall system should be accomplished by replication since a database server can’t be rescued if the physical disk breaks. I happen to agree with this philosophy but I am also aware that this isn’t a correct answer for everyone. So, what will I do with BlitzDB?

Several relational database hackers have pointed out that BlitzDB isn’t any safer than MyISAM since it doesn’t guarantee crash safety. This is currently true but I plan on making BlitzDB much safer than MyISAM by providing following features.

1. Auto Recovery Routine (startup option)
2. Tokyo Cabinet’s Transaction API (table-specific option)

The …

A live recording of my LinuxTag 2010 presentation entitled Storage Done Right: Building a Resilient, Distributed, Highly Available Open Source iSCSI SAN is now available from our web site. If you want to find out how to build a complete SAN from 100% open source, do take a look!

I do apologize for the less-than-optimal sound quality. I did the recording myself with my laptop mike, so unfortunately there’s quite a bit of clipping in the audio track. I hope my ramblings are still somewhat audible.

…

Just as a quick reminder, as LinuxTag 2010 in Berlin is going into full swing: I am speaking on highly available, distributed, open source storage this Friday in room Europa I at 4pm CEST.

If you’re in Berlin, drop by! Admission is free.

…

I just got word that a talk about iSCSI High Availability with Pacemaker and DRBD, which I submitted for LinuxTag 2010, has been accepted by the selection committee.

The presentation is entitled Storage Done Right: Building a Resilient, Distributed, Highly Available Open Source iSCSI SAN and I will talk in the Storage track, in English. Questions in German, of course, won’t be a problem.

As the conference organizers have asked speakers not to publicize the temporary schedule (for obvious reasons — hey it’s temporary), I can’t give the exact time and location yet. But if you want to hear about how you can replace your six-figure SAN with something much more open, much less locked-in and much less expensive, plan a trip to Berlin in early …

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 …

This Thursday (March 4th, 15:00 UTC - slightly later than usual), Robin Schumacher will present MySQL Column Databases. If you're doing Data Warehouse with your databases this is a must-attend, but it's also interesting to learn what typical other scenarios there are for using column-based storage engines, and how column databases work in the first place.

For MySQL University sessions, point your browser to this page. You need a browser with a working Flash plugin. You may register for a Dimdim account, but you don't have to. (Dimdim is the conferencing system we're using for MySQL University sessions. It provides integrated voice streaming, chat, whiteboard, session recording, …

This Thursday (March 4th, 15:00 UTC - slightly later than usual), Robin Schumacher will present MySQL Column Databases. If you're doing Data Warehouse with your databases this is a must-attend, but it's also interesting to learn what typical other scenarios there are for using column-based storage engines, and how column databases work in the first place.

For MySQL University sessions, point your browser to this page. You need a browser with a working Flash plugin. You may register for a Dimdim account, but you don't have to. (Dimdim is the conferencing system we're using for MySQL University sessions. It provides integrated voice streaming, chat, whiteboard, session recording, …

This Thursday (March 4th, 15:00 UTC - slightly later than usual), Robin Schumacher will present MySQL Column Databases. If you're doing Data Warehouse with your databases this is a must-attend, but it's also interesting to learn what typical other scenarios there are for using column-based storage engines, and how column databases work in the first place.

For MySQL University sessions, point your browser to this page. You need a browser with a working Flash plugin. You may register for a Dimdim account, but you don't have to. (Dimdim is the conferencing system we're using for MySQL University sessions. It provides integrated voice streaming, chat, whiteboard, session recording, …