Hi James Answer below, > While monitoring it, the output of: > > gluster volume rebalance pfs-rw1 status > > gives something similar to: > > rebalance step 1: layout fix in progress: fixed layout 4865 > > What does the number (in this case) 4865 represent, and what exactly does > "layout" refer to? > > First, the number represent the number of directories. About 'layout', as Joe mentioned, its the information about how the hash ranges are spread in the volume for particular directory. Let me try to make it more clear. Assume you have a distribute volume with 4 bricks (even a distribute-replicate volume will have distribute and layout still holds good). Now, when you create a directory, it gets created in all the 4 bricks, and now, when a file has to be created in that particular directory, it has to go in one of the 4 bricks. This decision is based on 2 things. One is the 'hash' value of the basename of the file. second is the information on which hash range should go to which brick (which is preserved in directory and we call it 'layout'). Now, when 2 more bricks gets added, the directory structure gets self-healed in that, but if you create the files inside the directory (existing directory), it will still be distributed in only earlier 4 bricks, and will not goto the newly added bricks. This is because the layout structure is static for a given directory. Now, when we do 'rebalance' we have to first fix this layout information so that the files can actually go to newly added nodes. That is done by an internal command, and once this happens, all the file stat information which are already cached will get revalidated (and you see a log in client log file for 'mismatching layout'). Hope this answers some of the questions. I will try to come up with the better documentation of the process and will get it added to the gluster wiki. Regards, Amar
