Im looking into RedHat GFS as a filesystem for a research paper. I was wondering if anyone knew how redundancy is implemented in GFS? Ive been doing some reading up on it but all i can find is that journeling can do something to do with recoery of data and that when a node fails the data from the node is fenced so it doesnt get accesses until the node comes back online. Im really interested in if it provides some kind of mirroring or block based raid across the storage nodes to maintain avaliability of all parts of the filesystem in the event of a failure. Does anyone know if this is possible. If not how does GFS do its high avaliablity configurations and how can it allow fulfilment of a SLA?