How are HDFS files getting stored on underlying OS filesystem?

Question

HDFS is logical filesystem in Hadoop with Block size of 64MB. A file on HDFS is in turn saved on the underlying OS filesystem say ext4 with 4KiB as block size.

To my

Answer 1

The retrieval speed from the ext filesystem isn't changed as you are thinking it very correctly. But what happens is a large file is split into pieces of 64Mb say which are stored on different machines.So when the retrieval call is made, multiple machines read the file pieces simultaneously and report to the main machine (Name node). This way things speed up. It is same like 10 men finishing a building task in 1 day rather than 1 man in 10 days.