We measured the time on the cluster required to cre- ate a FUSE group as a function of group size when group members are uniformly distributed throughout the system. We used group sizes 2, 4, 8, 16, and 32 and created 20 groups of each size. While group members were contacted in parallel, the more mem- bers there are, the greater the chance of including nodes at a significant network distance from the root node of the group. Note, for instance, that for groups of size 8, the 75th percentile time was significantly larger than the me- dian, whereas for groups of size 32, the 25th percentile, median, and 75th percentile are all relatively close, as with this many members the chance of encountering one or more slow communication paths is quite high.
In the simulator, we evaluated both a 400 node and a 16,000 node system. The simulated creation times fol- lowed the same pattern as those on the cluster, except that they tended to be about half as long, for the same reasons that the simulated and actual RPC times in Figure 6 for new connections also differed by about a factor of two. The group creation times for the simulated 16,000 node system were essentially identical to those for the 400 node
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