Reducing Disk IO


I have a ELK stack working right now. It receives around 80 docs per seconds from Logstah.
My monitoring tool graphs the number of operations per second made on the disk.
Here is what I get, around 35-40 operations/s :

What do you think of the purple graph (write operations) ? Does it look like a normal behavior ?
What are the options, in Logstash or Elasticsearch, that can reduce the number of operations ?

I found the option index.refresh_interval but I'm not sure if it could help.

Thank in advance for your help


Why does it matter? What problem are you trying to solve?