Thinking about storage class memory technologies hitting the market in the next calendar year. Technologies such as Intel Optane SSD Persistent Memory (3D Xpoint) will give users the ability to get extreme low-latency out of the file system layer.

MongoDB should think about improving its instrumentation by adding new latency buckets to track lower latency at the file system layer. 

For file system operations, the first bucket sits between 10-49ms. This first bucket will track latency of a file system on top of HDD, it doesn't do much for SSDs and it won't do anything for persistent memory. 

> db.serverStatus().wiredTiger.perf}{{ "file system read latency histogram (bucket 1) - 10-49ms" : 0,{{ "file system read latency histogram (bucket 2) - 50-99ms" : 0,}}{{ "file system read latency histogram (bucket 3) - 100-249ms" : 0,}}{{ "file system read latency histogram (bucket 4) - 250-499ms" : 0,}}{{ "file system read latency histogram (bucket 5) - 500-999ms" : 0,}}{{ "file system read latency histogram (bucket 6) - 1000ms+" : 0,}}{{ "file system write latency histogram (bucket 1) - 10-49ms" : 0,}}{{ "file system write latency histogram (bucket 2) - 50-99ms" : 0,}}{{ "file system write latency histogram (bucket 3) - 100-249ms" : 0,}}{{ "file system write latency histogram (bucket 4) - 250-499ms" : 0,}}{{ "file system write latency histogram (bucket 5) - 500-999ms" : 0,}}{{ "file system write latency histogram (bucket 6) - 1000ms+" : 0,}}{{ "operation read latency histogram (bucket 1) - 100-249us" : 0,}}{{ "operation read latency histogram (bucket 2) - 250-499us" : 0,}}{{ "operation read latency histogram (bucket 3) - 500-999us" : 0,}}{{ "operation read latency histogram (bucket 4) - 1000-9999us" : 0,}}{{ "operation read latency histogram (bucket 5) - 10000us+" : 0,}}{{ "operation write latency histogram (bucket 1) - 100-249us" : 0,}}{{ "operation write latency histogram (bucket 2) - 250-499us" : 0,}}{{ "operation write latency histogram (bucket 3) - 500-999us" : 0,}}{{ "operation write latency histogram (bucket 4) - 1000-9999us" : 0,}}{{ "operation write latency histogram (bucket 5) - 10000us+" : 0}}}