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Re: [Linux-cluster] GFS and server performance = Application



On Wed, 28 Nov 2007, isplist logicore net wrote:

In another thread, I was told that GFS would hurt performance and my thought
was that well, yes, it would take up some of the servers resources but there
should be plenty left over to handle web serving or what ever else the server
needs to serve up.

Is this a single-threaded or a multi-threaded test, and how is the node access distribution handled? GFS will primarily add latency (because locks need to be moved between the nodes). Once the node that needs to answer obtains the locks, it should be able to deliver full speed on data transfers. If you are accessing lots of small files, the latency will be very dominant to the bandwidth. This could be what you are seeing.

You also don't appear to have posted the results for the same app running off the local FS.

I've tested this in various ways today, from external connections, internal,
various httpd.conf settings, it's always the same. While some of the
httpd.conf settings have some effects, the biggest one is always what
application is being run on the server. In this case, Joomla seems to be
insanely resource intensive.

It could be down to how many files it accesses and how often. I've never used it, so I don't know. Remember that lock migration is expensive and requires cache flushes which will largely negate the usefulness of caching.

Gordan


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