Hello everyone I have a question regarding HDFS, data node code version 2.7.2. I have posted my question as Jira issue <https://issues.apache.org/jira/projects/HDFS/issues/HDFS-15206>.
I have observed that datanode issues sequential synchronous 64KB reads to local disk and add then send it to user and wait for the acknowledgement from the user. I was wondering why HDFS community did not use file mapping or asynchronous read from disk? This could allow disk scheduler to perform sequential reads from disk or perform read-ahead and prefetching. Is it something that could lead to performance improvement or not. I would appreciate if you could help me to find the answer to this issue from Hadoop community perspective. I asked from apache members and they told me that the version I am pointing to is old and this part of code written from scratch for modern SSDs. Could you please help me to find at which version this modification happened? and Where I can find it. Many thanks Mania
