Tuesday, April 20, 2010

Happiness is keeping it in RAM

Last week I deployed a new download.eclipse.org mega-machine.  If you haven't noticed, that's great.  The transition was completely transparent.

Reduced disk seek time on our file servers by maximizing file cache hits is what this is all about.  Here's a bandwidth graph of what our download server is sending to the Internet -- over 70 Megabits/sec (the green line) during the Eastern timezone daytime.

In return, this is what the download server is fetching from the NFS file server (the blue line).  You can see that as the server came online last week, the file cache was empty, and all the download requests needed to be fetched from NFS.  But today, NFS is serving less than 5 Megabits/sec to the download server.

70 Megabits out, 5 Megabits in.  Good cache hits there.

But in practice, since our bandwidth is limited, you won't see a faster download speed.  But your download should start instantaneously.  However, the biggest gain is achieved for services that need to use the NFS file server, such as CVS, SVN and Git.

But this is only the beginning ... wait until you see what we're doing with the MySQL database servers...


Anonymous Karl Matthias said...

Nice! That is a pretty good cache hit rate there. And all without configuring anything. ;)

6:33 PM  

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