&quot;we have a particular use-case where we have a large contiguous array with, say, 100,000 lines and 1000 columns&quot;<p>This is where they lost me. This is NOT a lot of data. Should we be surprised that memory-mapping works well here?<p>Below about 100-200 GB you can do everything in memory. You simply don&#x27;t need <i>fancy</i> file-systems. These systems are for actual big data sets where you have several terabytes to several petabytes.<p>Don&#x27;t try to use a chainsaw to cut a piece of paper and then complain that scissors work better. Of course they do...