Okay so the 4 nodes thing is a kind of exception? What about 8 nodes with redundancy 4? I made a table to recap possible configurations, can you take a quick look and tell me if it's OK? Here: https://gist.github.com/olivierlambert/8d530ac11b10dd8aac95749681f19d2c On Tue, Feb 7, 2017 at 4:18 PM, Jeff Darcy <jdarcy@xxxxxxxxxx> wrote: >> So far, I can't create a disperse volume if the redundancy level is >> 50% or more the number of bricks. I know that perfs would be better in >> dist/rep, but what if I prefer anyway to have disperse? >> >> Conclusion: would it be possible to have a "force" flag during >> disperse volume creation even if redundancy is higher that 50%? > > The problem is that the math behind erasure coding doesn't work for all > fragment counts and redundancy levels. To get two-failure protection > you need more than four bricks. If you had multiple disks in each > server you could get protection against multiple disk failures, but you > still wouldn't have protection against multiple server failures. The > only thing your "force" flag could do is allow placement of multiple > fragments on a single physical disk, but then you wouldn't even have > protection against two disk failures. If you want higher levels of > protection you need more disks, either to satisfy the mathematical > requirements of EC or to overcome the space inefficiency of replication. _______________________________________________ Gluster-users mailing list Gluster-users@xxxxxxxxxxx http://lists.gluster.org/mailman/listinfo/gluster-users
