[Linux-cluster] GFS and server performance = Application

[gordan at bobich.net]

On Wed, 28 Nov 2007, isplist at 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