I just did my first test-run of a Hadoop cluster on Amazon EC2. It’s not as tricky as it appears, although I ran into some snags, which I’ll document here. I also found these pages helpful: EC2 on Hadoop Wiki and manAmplified.
First, make sure the EC2 API tools are installed and on your [...]
Back in February, in a slightly plaintive post, the W3 sysadmins asked that people stop hammering their servers with requests for XHTML DTDs. Everyone said yes, this is a stupid problem that wouldn’t have happened if a) the XML spec were less dumb, or b) XML libraries were less dumb.
After that post, I spent [...]
Paul Johnson, in the U.K., wrote a piece about how there is no known “process” for programming. At some point, all the theory and methodology goes out the window and someone has to sit down, think about the problem, and write some code.
I’m sure I won’t be the only one to suggest this, but I [...]
The things I don’t know about Java… could fill a book. Here’s a new one, from the Hadoop sources:
public ArrayWritable(Class valueClass) {
// …
}
public ArrayWritable(Class valueClass, Writable[] values) {
this(valueClass);
this.values = values;
}
The second constructor uses the syntax this(arg) to call a different constructor, then follows with initialization code [...]
Joel Spolsky complains that architecture astronauts are taking over at big, rich companies like Google and Microsoft, pushing out elaborate architectural systems that don’t solve actual problems.
He’s right in that smart, technical people like to take on any large, abstract problem that is, as he puts it, “a fun programming exercise that you’re doing because [...]
My PC-oriented brain says it’s easier to work with a million small files than one gigantic file. Hadoop says the opposite — big files are stored contiguously on disk, so they can be read/written efficiently. UNIX tar files work on the same principle, but Hadoop can’t read them directly because they don’t contain [...]
I just discovered the paper The End of an Architectural Era (It’s Time for a Complete Rewrite), about re-designing database software from the ground up. It contains some unsurprising predictions — “the next decade will bring domination by shared-nothing computer systems, often called grid computing” — and some interesting ideas:
Any database smaller than 1 TB [...]
I just ran my first Amazon EC2 instance. Kind of a heady feeling, having nearly unlimited computing power just a few keystrokes away. I got the same feeling the first time I logged in as root on a dedicated web server.
I gotta say, though, that the ticking meter — even at just $0.10/hour — will [...]
I think I’m starting to get a handle on how Hadoop is supposed to work. The MapReduce model isn’t what troubles me. The mind-bending part is that there is no database. Everything happens by scanning big files from beginning to end. It’s like everything I learned about data structures with O(log n) access no [...]
An interesting scenario from Doug Cutting: Say you have a terabyte of data, on a disk with 10ms seek time and 100MB/s max throughput. You want to update 1% of the records. If you do it with random-access seeks, it takes 35 days to finish. On the other hand, if you scan [...]