Performance Difference between files getting opened with IoContext.RANDOM vs IoContext.READ

Hi Lucene Experts,
I wanted to understand the performance difference between opening and
reading the whole file using an IndexInput with IoContext as RANDOM vs READ.

I can see .vec files(storing the flat vectors) are opened with RANDOM and
whereas dvd files are opened as READ. As per my testing with files close to
size 5GB storing (~1.6M docs with each doc 3072 bytes), I can see that when
full file checksum validation is happening for a file opened via READ
context it is faster than RANDOM. The amount of time difference I am seeing
is close to 50%. Hence the performance question is coming up, I wanted to
understand is this understanding correct?

Thanks
Navneet