Hi all, Because of some testing/modification for the pull request that Andrew submitted, I tested some IO speeds for FLASH, which I decided to share here. What it came down to was testing a full dataset read, with slicing, versus constructing the H5S and only reading the 8x8 slab in question. I ran this with 30 iterations on the cluster merger FLASH dataset. Constructing a slice and only reading that in 2.x: 1.212s per slice Reading the full block dataset and discarding all but the slice of interest: 1.283s per slice In 3.0: 0.4856s per slice Mind you, seems like we have a big performance regression for finding the location of the most dense point, but that should be easily fixable. The vast majority of the savings come from pushing the selection of points *inside* the IO function, which lets us retain the H5D handles in between IO calls. -Matt