Intrepid Blog

I’ve written a small benchmark for couchdb to test it’s document creation performance. A script creates documents in total using bulk update to create at the same time with concurrent threads. The following graph show the time it takes to create an amount of documents against that amount of document for different values of with .

And for (two concurrent threads. Tested on a dual core machine)

The values of B are 1, 2, 4, 5, 8, 11, 16, 22, 32, 45, 64, 90, 128, 181, 256, 362, 512, 724 and 1024

As you can see, a higher value of causes the graph to shift to the right which means more for the same time. Bulk update really does make a difference. Or non-bulk-update really sucks. Also adding threads does help a bit, but not as much as expected.

There are some more interesting graphs to plot ( against ). More graphs tomorrow.

(For those interested, the raw data from which these graphs were plotted.)

CouchDB is a non-relational database which uses MapReduce inspired views to query data. There are lots of cool things to tell about its design, but I rather want to talk about its performance.

Today I’ve been busy hacking together a little script to import all e-mails of a long e-mail thread into a couchdb database to write views to extract all kinds of statistics. I already imported these e-mails into a MySQL database a few months ago, but was quite disappointed by the (performance) limitations of SQL. The e-mail thread contains over 20,000 messages which weren’t a real problem for MySQL. When importing, however, couchdb was adding them at a rate of only a few dozen per second with a lot of (seek)noise of my HDD.

So I decided to do a simple benchmark. First of, a simple script (ser.py) that adds empty documents sequentially. It’s averaging 16 per second. It occurred to me that couchdb waits for a fsync before sending a response and that asynchronously the performance would be way better. A simple modification to the script later (par.py) it still averaged 16 creations per second.

I guess, for I haven’t yet figured out how to let straces tell me, that it’s the fsync after each object creation which causes the mess. couchdb itself doesn’t write or seek a lot, but my journaling filesystem (XFS) does on a fsync.

Can anyone test it on a different filesystem?

Update Around 17/sec with reiserfs.

Update I had some trouble with the bulk update feature. I switched from svn to the 0.7.2 release. I got about 600/sec, which dropped to a steady-ish 350/sec when using sequential bulkupdates of 100 docs. Two bulk updates in parallel yield about 950/sec initially, dropping to 550/sec after a while. Three parallel updates yield similar performance.