I have been thinking about why Red Hat purchased the Gluster parallel file system in October 2011. Back in December 2003 Red Hat purchased the GFS file system. GFS did not work out that well for Red Hat. It never added many features and it did not provide scaling. GFS is a totally different type of parallel file system than Gluster. Gluster does not support multiple threads opening and writing to the same file, often called N to 1 (1 file with N threads writing).
On the other hand, Gluster is very good at multiple writes to the file system from multiple threads, which is often called N to N (N thread writing to N files). So you might ask what types of applications do that type of I/O. The one that comes to mind, and the one I think drove Red Hat to buy Gluster, is video surveillance.
This is a large and fast growing market where the market demands very low-cost storage and software and a scalable software stack. Take a casino or a city police force. Each camera, and there are hundreds of them, is writing to a different file, but they want all the files in a single namespace. You might say, why not just buy a bit NAS box? Remember, I said they wanted to do this as inexpensively as possible, and they need scalability. NAS boxes generally do not scale linearly as a shared file systems does by adding servers and storage. This video surveillance market is growing fast, and it will continue to grow as more and more cameras are moving to digital online storage, as compared to writing to DVD or tape.
So why did Red Hat buy Gluster? My guess is that Red Hat wants to eventually take on the NAS players in the part of the market.