Recommendations for Bugzilla hardware

[David Miller]

Eddie Xie wrote:

> I see that you have your Bugzilla using dual processor systems.  How
> much of a benefit is it to have two processors?  Do you have to do
> anything special to get this benefit (e.g., use a specially compiled
> version of MySQL, or use a specialized version of Linux or FreeBSD).

You need a kernel that was compiled for "SMP" or "Symmetric 
Multi-Processing".  Most linux distros these days have such a kernel 
already compiled for you in one of the kernel packages (I know Red Hat, 
Debian, Fedora, and Ubuntu all do, I haven't used many others).

It's a great benefit to a machine with Apache and MySQL on the same box, 
because then essentially, MySQL gets one and Apache gets the other (not 
exactly, but that's the general idea).  In the case of having just the 
webserver on that box, Apache can basically handle twice as many 
requests at once because it has both processors to split the load between.

> What is the benefit of using a replicated database for queries?  Is it
> only when multiple queries are going on at the same time?

When you send an update to a table, the table gets locked for a brief 
moment, preventing queries from accessing that table (MySQL doesn't have 
row-level locks unfortunately -- not in the current versions we support 
anyway).  So every time someone updates a bug, anyone running a query is 
going to be put on hold momentarily.  If lots of people are changing 
bugs at once, this leaves very little time for queries to run.  The 
replicated database is set up with "low-priority writes," meaning that 
queries get priority, and updates are done whenever there aren't any 
queries running.  If there's a LOT of people running queries, it's 
possible for the replicated database to get a little bit stale, but it 
keeps everyone running quickly, and it usually doesn't stay behind for 
very long.

-- 
Dave Miller                                   http://www.justdave.net/
System Administrator, Mozilla Foundation       http://www.mozilla.org/
Project Leader, Bugzilla Bug Tracking System  http://www.bugzilla.org/