Atlassian Crucible very slow on large repository

Since migrating to MySQL made a noticeable difference for some repositories, consider tuning the database for further improvements. Changing some my.cnf values from the defaults can make a huge difference. See InnoDB Performance Optimization Basics for more information. Also check for slow queries by enabling the slow query log and add indexes where appropriate.

My next guess would be network speed: is your Crucible instance on the same wired local network as your SVN repositories? You might also try giving Crucible a trial run on the same machine as your primary repository if possible to eliminate network latency as the culprit.

And I know it might be difficult depending on your work environment, but running Crucible in a VM probably isn't helping things; Atlassian makes a note of this on their very brief Best Practices for Crucible Configuration page. I'm sure you've already come across it, but I'll also mention the Tuning FishEye page for other readers.

I also have performance issues for large projects, but attribute a lot of the slowness to Crucible's heavy web interface. This is especially true after clicking around for a bit (previously viewed pages in a review remain in the browser window, even when hidden from sight). Our developers have noticed a slight speed increase by switching to Google Chrome. Also check out the Atlassian IDE Connector if a compatible plugin exists for your development environment. The Eclipse IDE Connector had issues of its own the last time I used it (many months ago), but it could at least handle large file sets without hanging up.

Depending on your company's development practices, you could stop scanning a large number of code branches (assuming many of them are no longer active), and disable repositories for completed/dead projects until they're needed. My company utilizes very small teams on a large number of projects, so most of the time we work primarily on trunk, making branches the exception; we therefore explicitly add branches to scan instead of including all branches by default. Also make sure you're not accidentally scanning tags.

How is your CPU usage on the Crucible box? If you're using SVN behind Apache HTTPD, examine how many connections are consumed by Crucible during a big repository scan. Aside from that, I'm not sure what else you could look at (maybe disk speed? Repository scan frequency?), but hopefully the above tips will help a bit.